Try using the Last Known Good Configuration.
To start your computer by using the Last Known Good Configuration feature, follow these steps:
1. Start your computer.
2. When you see the "Please select the operating system to start" message, press the F8 key.
3. When the Windows Advanced Options menu appears, use the ARROW keys to select Last Known Good Configuration (your most recent settings that worked), and then press ENTER.
4. If you are running other operating systems on your computer, use the ARROW keys to select Microsoft Windows XP, and then press ENTER.http://support.microsoft.com/kb/307852
If this doesn't work and you have the installation CD for the operating system try using the Recovery Console.Note
: You may need to change the boot order in the BIOS so that the CD-ROM is the first device in the boot order to be able to boot from the Windows installation disk
.To run the Recovery Console from the Windows XP startup disks or the Windows XP CD-ROM, follow these steps:
1. Insert the Windows XP startup disk into the floppy disk drive, or insert the Windows XP CD-ROM into the CD-ROM drive, and then restart the computer.
Click to select any options that are required to start the computer from the CD-ROM drive if you are prompted.
2. When the "Welcome to Setup
" screen appears, press R
to start the Recovery Console
3. If you have a dual-boot or multiple-boot computer, select the installation that you must access from the]Recovery Console.
4. When you are prompted, type the Administrator password. If the administrator password is blank, just press ENTER.
5. At the command prompt, type chkdsk /r , and then press ENTER.
6. To exit the Recovery Console and restart the computer, type exit at the command prompt, and then press ENTER.