System lockup-Windows 2K during startup

I have a Gateway E-4200 that locks up during startup. Windows 2K has aready been reinstalled and format set to NTFS. All hardware has checked okay and replacecement of the video driver does not help. Will only lockup with cold boot. Will not lockup with warm boot. Will boot okay after rebooted, but not after more than 30 minutes.
Locks up after the startup screen with the progress bar and before Ctrl-Alt-Delete prompt.