I don't know if this has happened to anyone else, but after upgrading my copy of Nero I found, much to my surprise, that Windows would no longer boot. It'd fill its little progress bar and just spontaneously reboot. After a bit of head scratching I realized that I might have some luck restoring a previous config.
Should anyone else face this problem, try the following:
1. Allow it to get to the bootloader menu (should you have one). With Win2000 selected press F8 and choose "Last Known Good Configuration."
2. On the next screen, select the hardware config you use most often (usually there's only one anyway) and press Enter.
3. At this point you should be able to log in normally. Open Regedit and go to the key
HKLM/Software/Microsoft/Windows/Current Version/Run
and delete the "NeroCheck" key.
I'm not certain just why it causes the machine to reboot (it doesn't make an entry in the event log or anything), so it's a mystery. Oh well, just thought I'd share.
