This article applies to Windows Vista and Windows 7 only.
Windows 8 users should read this article instead.
Windows XP users should use Recovery Console for fixing errors on hard disks.
When you cannot even get into Safe Mode, then most probably there are some errors or missing files on your hard disk that prevent Windows Vista or 7 from starting correctly.
Repair Your Computer is a set of tools for recovering from Windows such errors and it is available on Windows installation DVD. Windows 7 users can also create a System Repair Disc, or borrow one from friends - as long as the hardware architecture (32-bit/x86 or 64-bit/x64) matches.
Windows 7 user might be able to launch Repair Your Computer or Startup Repair from a hidden system partition. The two options are described in the end of the current article.
You can also download Windows 7 Professional (with Service Pack 1) installation DVD from DigitalRiver (64-bit / x64 edition or 32-bit / x86 edition) using your friend's computer and burn the ISO image to DVD with Windows 7 Disc Image Burner or CDBurnerXP. But do not use the disc for fixing Windows Vista installations!
If you do not have the disc (a common case for computers that had Windows Vista or 7 pre-installed) and your friends do not have a matching one either, you can use my Data Recovery CD/USB for fixing errors on disk or repairing Master Boot Records (MBR), but other options of Repair Your Computer are unavailable.
Do not use Windows 7 DVD for repairing Windows Vista installations, or vice versa! You can only use the Command Prompt option on the disc to fix file system errors.
If you can borrow a correct Windows installation DVD from a friend, make sure you get the right version: you can only use 32-bit Windows disc for repairing 32-bit Windows installations and 64-bit Windows disc for fixing 64-bit Windows installations!
Windows Vista had the same option (called Windows Vista Recovery Disc) until Service Pack 1 was released, but somehow Microsoft decided to disable this feature later. The file is still there, but launching it does absolutely nothing. Restoring a pre-SP1 version ends up with asking for Windows Vista installation DVD - so it is a dead end for those who never got the media.
Those in desperate need for the Windows Vista or 7 Repair/Recovery Disc can pay $9.75 and download one from SystemDiscs. Make sure to download the correct version (32- or 64-bit) of the disc!
Repair your computer option using Windows Vista or 7 DVD/System Repair Disc
If your computer does not boot from DVD, read the Computer boot order on how to change boot order.
After you boot your computer using Windows DVD or System Repair Disc, a black screen appears with gray text "Press any key to boot from CD or DVD". Press some key on your keyboard (Space and Enter are the most common ones 
) within 5 seconds to launch Windows from the disc.
Windows will load some files from the disc, this takes time.
If using Windows Vista/7 installation DVD, Install Windows dialog appears. Select your preferred settings from Time and currency format and Keyboard or input method boxes. I suggest you leave Language to "English" here to better understand this article.
If using Windows Vista/7 System Repair Disc, System Recovery Options dialog appears instead. Here you can only select the appropriate keyboard layout.
Click Next to continue.
Windows installation media users will see a big tempting Install now button. Do not click it! Click Repair your computer in the lower left corner instead.
System Repair Disc skips this step and continues with looking for Windows installations.
Recovery environment will then look for present installation(s) on hard disks. This might take up to a few minutes.
Click Next after the correct installation has been detected. If you have multiple versions of Windows installed, click the one that is broken.
If you see nothing listed here, your computer has a disk controller that Windows Vista or 7 is not able to detect by default. Click Load drivers, insert the CD, floppy disk or DVD that came with your computer or disk controller and load appropriate drivers from there. Your Windows installation will then be located.
If you have several user accounts on the computer, you might have to log on using the account that has administrative rights. Select an administrator's user name and enter the password.
System Recovery Options window then appears with the list of available recovery tools. The tools are almost identically named in Windows Vista and 7.
Let's see an overview of the tools next.
Please note that if you are using a wrong media here - e.g. Windows Vista installation DVD on Windows 7 PC, or 32-bit version of System Repair Disc on 64-bit Windows - you are able to use the Command Prompt option only. While the other options are not disabled in the list, using these end with error messages and might damage your broken Windows installation even more.
Step 1 - Startup Repair in Windows Vista or 7
The very first option to try in case Windows is unable to boot is the Startup Repair (see the two pictures above). Startup Repair will check the condition of your hard disk and see if files needed to launch Windows are present. The process takes several minutes to half an hour.
If a problem is found, Startup Repair will try to fix it. This usually takes a few minutes for minor problems, but sometimes the repairs might last for up to half an hour.
In case problems were fixed successfully, Startup Repair offers to restart your computer immediately to see if your Windows starts normally now. Often it does!
In rare cases, Startup Repairs launches again automatically and does some more fixing. Let it finish its job and Windows should start normally after the next restart.
In case Startup Repair was unable to locate or repair problems, you will see one of the following screens. You can click Finish to close Startup Repair and then try some other method of restoring. Or you can click View advanced options for system recovery and support to return to the list of recovery tools.
After an unsuccessful repair of Windows 7, Startup Repair suggests using System Restore for fixing your computer. If Startup Repair was your first step in fixing Windows 7 problems, I suggest you click Cancel here and try other recovery tools first.
If you've tried all other tools already, click Restore button. Please remember that this System Restore operation cannot be undone - you will not lose your documents, e-mails, pictures, videos and other personal data, but some programs might be removed during the operation. Read this tutorial about System Restore for detailed instructions.
After clicking Cancel, Microsoft asks to send some information about the problem to their servers to help creating solutions for such situations. This will not send your personal information to Microsoft, just data about your computer configuration and problems not repaired.
If you are really concerned about your privacy, click Don't Send. If you would like to help Microsoft a bit, click Send information about this problem (recommended).
Step 1.1 (optional) - use Command Prompt for fixing disk errors
If you do not have the correct Windows installation/System Repair media, but you still need to check for and fix errors on disks, click Command Prompt in the list.
A black Command Prompt window opens on drive X. The X: is a special temporary disk created entirely in the Random Access Memory (RAM) of your PC. No hard disk space is used for this drive.
First, we need to locate the drive where Windows is installed. Most probably this is a drive with letter C, D, E or F.
Type c: and press Enter. This will open a partition/volume with drive letter C.
Now type dir win* and press Enter. This lists all files and folders that have names starting with "win", such as windows, winvista, win7, etc.
As you see, nothing was found in the example below. The second line states that volume label is "System Reserved", this means that this is a hidden recovery partition that new installs (not upgrades) of Windows Vista and 7 create. You do not need to use or check this partition. Not all computers have such partition.
If no matches appeared, change to drive D by typing the command d: and pressing Enter. Then repeat the dir win* command (or press the Arrow Up key twice) and see if there is a matching folder on the disk.
In the example below, there is a folder named Windows. The <DIR> indicates it is a folder (directory). Most probably this is the drive where Windows is installed.
Sometimes files are badly messed up on a drive and the dir command ends with an error message. This certainly means that you must check this partition/volume.
Now type chkdsk <the drive letter>: /F /X and press Enter. Replace <the drive letter> with the letter of drive where Windows is installed (or the drive that has files badly messed up), for example chkdsk d: /F /X or chkdsk c: /F /X.
This command will find and repair errors on the partition/volume (the /F switch) and if required, unmount it first (the /X switch).
If you want to run a full disk check with recovering data from unreadable clusters, use the chkdsk <the drive letter>: /R /X command instead. Note that the exhaustive test might take several hours to complete.
The process might take quite a while (up to an hour). After it is completed, verify that there is a line stating "Windows has checked the file system and found no problems" in the report. If there were errors on the volume, repeat the last command until the no problems message appears.
Ignore any failure messages about event log.
After checking the disk, close Command Prompt by clicking the X mark on the top right. If there were errors detected, click Restart in the System Recovery Options menu and try starting Windows normally and see if the problem has been solved.
Step 2 - Windows Memory Diagnostic Tool
If Startup Repair did not solve your problems, and you have not used free Memtest86+ for checking if your computer's memory modules are fine, try Windows Memory Diagnostic. This will ensure that Random Access Memory (RAM) modules do not cause computer problems. A faulty module is the most common reason for software crashes and lockups.
Please note that this check will take at least 30-40 minutes to complete.
Click Restart now and check for problems (recommended) in Windows Memory Diagnostic dialog.
After your computer restarts, Windows Memory Diagnostics Tool will launch automatically. The test will easily take 40 or minutes. If your computer reboots or stops responding during the test, you should replace memory modules in your computer. Consult the computer reseller and the manual that came with your computer for this.
Check the Status column from time to time. If it says "No problems have been detected yet", your computer's memory is working fine.
After the lengthy test is complete, your computer will restart. In case the Status was "No problems..." before the restart, you should boot from Windows DVD or Repair Disc again and return to Repair your computer tools.
In case Windows Memory Diagnostic detected problems in memory modules, you should replace memory modules in your computer as soon as possible - the faulty module(s) can easily recreate the problems and in the long run you will definitely experience data loss! Consult the computer reseller or the manual that came with your computer for replacement of memory modules.
Do not use your computer or try other recovery options until the memory modules have been replaced!
Step 3 - System Restore
The next step is to try System Restore from System Recovery Options menu. This works only while using the correct Windows installation or System Repair disc. Using Windows 7 media on Windows Vista installation (or vice versa) ends with an error message about no available Restore Points.
Please note that this System Restore cannot be undone (but you can still choose another Restore Point later). While you will not lose any of your documents, pictures, videos, e-mails, etc, all programs installed after the selected Restore Point will be deleted. You will have to reinstall these.
Read detailed instructions on using System Restore in this article.
Step 4 - other options
In case nothing helped, you must restore the disk image backup of your computer. You do have a backup, don't you?
- If you are using Windows Vista or 7 built-in backup, you can click Windows Complete PC Restore or System Image Recovery in System Recovery Options menu and try restoring a disk image backup. Detailed instructions on Windows 7 System Image Recovery are available in this article.
- If you are using EaseUS Todo Backup Free, read this article about restoring disk image using bootable emergency disc.
In case you do not have a backup, you can use my Data Recovery CD/USB or Puppy Linux to copy your documents, pictures, videos, music, etc to a flash drive or external hard disk. After copying is complete, reinstall Windows and all programs, copy your rescued files back to your computer and do start making regular backups this time.
Other ways of launching computer repair in Windows 7
Windows 7 users can also run Repair Your Computer or Startup Repair from a special hidden partition on hard disk.
1. Launch Startup Repair offered at computer startup
The Launch Startup Repair option is offered automatically after Windows 7 detects that it failed to start the last time. If the failure happened just once due to power failure during Windows startup, you can ignore the offer by pressing Arrow Down key on your keyboard to select Start Windows Normally instead and then pressing Enter key.
Otherwise, you should use Launch Startup Repair (recommended) option.
Move up to Startup Repair section.
2. Repair your computer in Windows 7 Advanced Boot Options menu
To access the whole set of recovery tools without using the Windows 7 installation DVD or System Repair Disc, you need to open Advanced Boot Options menu right before Windows 7 starts. After you power on your computer, you might see some full-screen logo or black screen with gray texts such as "AMI", "Intel", "Testing Memory", "Hard disk", etc. Press F8 key on your keyboard repeatedly right after you see such screen disappear. This will open Windows 7 Advanced Boot Options menu. If you see some Select Boot Device menu instead, press Esc key to hide it and then press F8 key again a few times.
Use arrow keys on your keyboard to select Repair Your Computer and press Enter key to confirm your selection.
Move up to Repair your computer section for detailed instructions on using the tools.
