Windows 2k and XP are set to reboot on error by default. Can you get into safe mode on your system?
Hit f8 on post until you see a screen that will allow you to boot into safe mode. Once there you should check to see what monitor type you have installed. If it's anything besides "plug and play" or "default" then you will want to change this to one of these, or remove it all together.
As for the automatic reboot on error (this means BSOD) you can change this setting by right clicking on the "my computer" icon, then goto "properties". From there look for "advanced", then "startup and recovery". Half way down the screen you will see a setting for "system failure" and a box for "automatically restart". unclick the checkmark in the box. Now you will see the BSOD when it comes up and windows will not reboot on you- shouldn't reboot that is. :-)
I have no idea why microsoft decided to ship thier OS's with this setting enabled...
Anyways, hope this helps!