Details are missing so I'll only be able to share generic and usual fixes rather than what may be specific to your hardware and OS.

1. Remove the registry keys noted at http://support.microsoft.com/kb/270008
Sorry I will not write the long version why you do this.

2. Run AUTOFIX from http://www.jsifaq.com/SF/Tips/Tip.aspx?id=6952 to fix other entries.

Of course 2 bad drives (dead lasers) could cause this. The test is simple. Try to boot from your XP Pro CD.

Bob