This is a shot in the dark. What you can try is using the repair tool on your Windows XP disk. We can use some tools on the disk to help identify and possibly fix problems with your startup. Startup files, boot tables and sectors, and critical Windows bootup files can get corrupt during hard shutdowns, interrupted startups and shutdowns, new hardware installations where new drivers were added but not saved for a reboot, etc.
First I would check the integrity of your drive and the data of your drive. Follow the below instructions:
1) Place your Windows XP CD in the drive and boot from your CD drive (change boot up priorities in your BIOS if needed)
2) Allow the computer to boot the CD and load all the windows drivers.
3) When given the option, select "R" for repair:
4) When you get to the Command Prompt, Select the drive your Windows Installation is on (probably C:\Windows):
Now, we will use two commands to help ensure the data on your drive and the windows installations or intact. First we'll do drive table integrity:
a) Type "chkdsk c: /p /r" and let that run. (assuming C: is your primary root directory. If the computer found errors then I'd suggest rerunning chkdsk until it finishes running with no errors to correct.
b) Type "bootcfg" with one of the following switches:
/add Adds a Windows installation to the boot menu list.
/rebuild Iterates through all Windows installations so that you can specify which installations to add.
/scan Scans all disks for Windows installations and displays the results so that you can specify which installations to add.
/default Sets the default boot entry.
/list Lists the entries already in the boot menu list.
/disableredirect Disables redirection in the boot loader.
/redirect Enables redirection in the boot loader, with the specified configuration.
So for example, you may want to type "bootcfg /scan" to see if it can find a windows installation. Type "bootcfg /list" to list the ones it found, if any. If it didn't find any, then your Windows installation is probably screwed and you'll have to reinstall Windows. If it finds one, then ensure it's added to your boot menu list by using "bootcfg /rebuild" or "bootcfg /add" to ensure the correct Windows installation is setup to load on bootup.
If after these are fixed and you still have issues you might try to fix your MBR. To do this, follow the same instructions as above but instead of steps a)/b), start below:
c) Type "fixmbr" and let it run. This will rewrite your master boot record to the boot sector.
Once complete, reboot your machine and see if Windows will load. If not and you still get a blank screen or you get some Boot Sector error, then repeat the above steps with the following modification for the last step:
d) Type fixboot and let it run. This will rewrite your boot sector and fixes problems if there was a previous corrupt boot sector.