OSX doesn't appear to have this issue
Ok, back to my windows hat...
If you can get to the recover console from your Windows Install CD, you can try a couple things.
First go to C:\windows\system32\config and copy the file named SOFTWARE to SOFTWARE.BAK. Delete the original SOFTWARE and copy SOFTWARE.BAK back to SOFTWARE. The copy process SOMETIMES fixes file corruption....
Reboot, if it still BSOD, then go back to the recovery console...
Now, go back to the config file and rename SOFTWARE to SOFTWARE.OLD.
now enter the following:
copy c:\windows\repair\Software c:\windows\system32\config\Software
This will restore the last saved Software hive. However, this is usually the old hive and you will need to reinstall all of your applications. Some of your other settings will be lost as well.
Once you've done this, I recommend backing up any essential files and rebuilding XP from scratch.