Service Packs are collections of security updates and stability enhancements from Microsoft. In Windows Vista and 7 you must download and install these one by one - first Service Pack 1, then Service Pack 2, etc.
The latest Service Pack for Windows Vista is Service Pack 2.
The latest Service Pack for Windows 7 is Service Pack 1.
How do I know which Service Pack I have on my computer?
Right-click My Computer icon on Desktop or in Start menu and choose Properties. Or use Windows Key+Break keyboard shortcut.
See what's written under Windows edition. First comes Windows Vista or 7 edition name (such as Ultimate, Home Basic, etc), then comes copyright information and then comes Service Pack information.
If you already have Windows Vista Service Pack 2 or Windows 7 Service Pack 1 installed, you can safely skip this article.
If you have Service Pack 1 in Windows Vista or no line about Service Pack at all, continue reading this article.
Those with no Service Packs installed in Windows Vista should also note if their Windows is a 32-bit or a 64-bit edition. See the line System type for this.
Close System Properties window by clicking OK.
Before installing a Windows Vista or Windows 7 Service Pack, please follow steps in the following articles - otherwise the installation might fail because of some trivial reason such as messed up files on system drive or not enough free space on disk, or some malware blocking installation:
- Check disks in Windows;
- Free up disk space in Windows (you need up to 5 gigabytes of free space to install a Windows Vista or Windows 7 Service Pack);
- Full anti-virus scan, such as avast! Free Antivirus on-demand scan or Microsoft Security Essentials on-demand scan;
- Full anti-malware scan, such as Malwarebytes' Anti-Malware on-demand scan;
- Optionally, create a disk image backup, as described in the Configure EaseUS Todo Backup Free in Windows article. Windows 7 users can also use the built-in backup tool for this: Configure automatic backup in Windows 7.
Installing Service Pack pre-requirements using Windows Update
Both Windows Vista and 7 have a long list of required software that must be installed before a Service Pack can be downloaded and applied. Therefore it is neccessary to install all available important updates first.
If you do not have Windows Update open yet, start by clicking Start button or pressing WINDOWS KEY, then type "update" in Search box and click Windows Update.
Click Check for updates on the left to see if new updates are available. This applies even if Windows Update claims "No important updates available".
If Windows Update will display some error page instead, try restarting your computer first. If this does not help, use this Fix It tool for repairing Windows Update problems.
If this is the first time you run Windows Update on Windows Vista or 7, you might see a lot of updates available. Click Install Updates button after the search is complete.
Large number of available updates also means that some updates cannot be installed because of conflicts - so a few failed updates is completely normal in such cases.
Please note that Windows Vista Service Pack 2 or Windows 7 Service Pack 1 will not appear on the list of updates until prerequisites have been installed! And remember, Windows Vista Service Pack 1 will not appear on this list anymore - if your Windows Vista has no Service Packs installed, you must download and install Service Pack 1 manually!
Click Continue or Yes in User Account Control dialog.
Wait until the installation is complete and restart your computer if required. Repeat the process until you see just one important update available for Windows 7 or Windows Vista with Service Pack 1 installed, or no important updates available for Windows Vista with no Service Packs installed.
To see which important and optional updates are available, click either <number> important updates are available or <number> optional updates are available.
All important updates are selected by default and there is no need to deselect them. These updates must be installed in order to receive Windows Vista or Windows 7 Service Packs.
To see and select other updates, click Optional tab on the left. Then select the updates you want to install and click OK. Then click Install updates and click Continue in User Account Control dialog.
Downloading Windows Vista Service Pack 1
To download Windows Vista Service Pack 1 manually, use one of the links below (click Run in Internet Explorer download prompt and then click Continue in User Account Control prompt after the download is complete):
- Windows Vista, 32-bit versions Five Language Standalone package for English, French, German, Japanese, or Spanish (Traditional)
- Windows Vista, 32-bit versions All Language Standalone package for all supported Windows Vista languages
- Windows Vista, 64-bit versions Five Language Standalone package for English, French, German, Japanese, or Spanish (Traditional)
- Windows Vista, 64-bit versions All Language Standalone package for all supported Windows Vista languages
Please remember that you will still have to install all updates available before applying Service Pack 1, as some of them are required for installing the Service Pack!
To see if you have 32-bit or 64-bit Windows Vista, use keyboard shortcut Windows Key+Break and see System type in System section.
Installing Service Packs in Windows Vista and 7
In the Windows Update window, click Install updates button and click Continue or Yes in User Account Control dialog. The Service Pack will then be downloaded. This might take up to an hour, depending on your connection speed.
In Windows 7, first part of the process will run in the same Windows Update window.
In Windows Vista, Welcome to Windows Vista Service Pack window opens. Click Next.
You can read the really fuzzy license terms if you want to (in short: you are responsible for everything 
). Click I accept the license terms and then click Next.
Finally click Install.
The installation of any Service Pack can easily take an hour or even more. You can safely do something else meanwhile.
After the installation is complete, click Restart now in the Windows Update window.
You expected the process to be complete, right? Not just yet - after you've been logged off, the installation will continue and it will go on after restarting your computer. Just wait for the process to complete, it still might take an hour now.
After Windows Vista or Windows 7 Service Pack installation is really complete, you will see Welcome Screen. Log on and re-run Windows Update to install all other updates released after the Service Pack.
If you just installed Windows Vista Service Pack 1, you must continue by installing some prerequisite updates to see Windows Vista Service Pack 2 available in Windows Update.
You might see a large increase in free disk space after installing Windows Vista Service Pack 2, this happens because old System Restore Points are deleted before installing Service Pack 2.
If everything works correctly after installing a Service Pack, you can free some disk space by removing Service Pack Backup Files using Windows Disk Cleanup. Please wait for at least a week before deleting the backup files - this ensures everything runs smoothly.
