How to fix my Dell Latitude D600?

The Windows installation seems to have been corrupted. Some key files are missing or corrupted and need to be replaced, but, in this case, it can't be done without reinstalling Windows XP, a process that will probably erase any data on the primary drive/partition.
If using the F8 key had worked, you'd have been able to go back to a previous restore point that would have hopefully restored the missing/damaged files.

First thing to do: Do a backup of your personnal data and collected files.
Get a Linux live CD and boot from it. The reduced Linux environment will NOT change anything on your hard drive.
It will allow you to access your drive. COPY all your data and files to an external drive.
Take note of your Windows activation key.
Get a Windows XP installation CD. You can get the links of an image (ISO) from most torrent sites if you don't have a genuine CD. Burn that image to a CD-R.
Reinstall Windows XP using your actual product key.
Reinstall your drivers.
Have Windows auto-update itself.
Reinstall your programms and applications.
Restore your data and personnal files.

Electro
December 2012