If your computer does not boot from CD, check this article to change boot order.
When you cannot even get into Safe Mode, then most probably there are some errors on your hard disk that prevent Windows XP from starting correctly. Here's where Recovery Console comes in handy. You need your Windows XP installation CD that came with your computer or, if you bought Windows XP from a shop, then it should be in the Windows XP box.
If you can't find your Windows XP CD, you can borrow one from your friends - any version of Windows XP should be able to boot into Recovery Console.
In Windows Vista and 7, the equivalent of Recovery Console is the Repair your computer option on Windows installation DVD; Windows 8 also has similar tools in its Recovery Environment.
Starting Recovery Console
Insert Windows XP CD to your computer's CD or DVD drive and restart the computer.
After your computer boots from the Windows XP CD, you'll see text "Press any key to boot from CD" for about 5 seconds. Press Y or Space on your keyboard, for example - but you can press really any other key.
After pressing some key on your keyboard, you will see blue screen and Windows XP setup program will load essential files and drivers from CD. It takes quite a while. Do not press any keys during that time.
After loading is complete, you will see a screen like this. Press R key on your keyboard to start Recovery Console.
After Recovery Console starts, there is a message at the bottom of the screen "To select non-default keyboard layout press ENTER now". This message is displayed for 5 seconds.
If you do have a standard US keyboard, wait until the message disappears.
If you do not have a standard US keyboard layout, press Enter key and select your keyboard layout by using up and down arrow keys and confirm your selection by pressing Enter again:
After this, Recovery Console will ask which Windows installation you want to use. Most probably you have only one Windows XP installed so press 1 on your keyboard and then press Enter to confirm the selection. If you press Enter without pressing a number key first, your computer will restart immediately.
Checking and repairing hard disks
The first thing to do is to find out which letters your computer has assigned to your hard disks and partitions on them. You will need drive letter or letters later on.
Type in the command map and press Enter to execute the command:
As you want to check your hard disks, look for rows containing \Device\Harddisk. In this example, I have only one hard disk mapped to drive letter C:, its file system type is NTFS, its total size is 20466 megabytes (or 20 gigabytes) and its address is \Device\Harddisk0\Partition1. The most important info is drive letter "C:".
The disk checking and repairing utility is called chkdsk, short for Check Disk.
To start checking and repairing, type in the following command: chkdsk c: /P
Then press Enter to execute the command.
This will check your hard drive. If you have more than one hard drive or partition, you must check these too by replacing the "c:" with "d:", "e:" or any other letter that your hard drive and partition has, see the map command above. For example, chkdsk d: /P or chkdsk e: /P.
Chkdsk will check your disk (this might take some time) and display a report after it finishes checking and repairing:
As you see from the row "CHKDSK found one or more errors on the volume", there were errors on the drive. It is very important to check the disk again when you see this message, because there might still be other errors on the disk.
So recall the last command by pressing arrow Up key on your keyboard once. Or you can also type the command chkdsk c: /P again. Press Enter to execute the command.
Repeat the checking and repairing process until you see report stating "CHKDSK has finished checking the volume". This means that the disk/partition is fine now.
Please remember to check all other hard disks and partitions, if you have more than one.
You can quit Recovery Console and restart your computer now by typing exit and pressing Enter on your keyboard.
Hopefully this solved your Windows XP starting problem. 
If not, see the Non-destructive reinstall of Windows XP article or use my free bootable Data Recovery CD/USB to solve additional problems or recover your files.
