A variation of this same error message exists as well in Windows 95 and 98, but is usually seen only during the boot process. It occurs sometime between when the autoexec.bat and config.sys files finish running, and when the Windows GUI is actually started, leaving you at a dull gray-on-white textmode console reading "Windows protection error. You will need to restart your computer.". Often, the screen will also be flickering with little orangish artifacts of some sort. Usually, once a system begins to display this, it's b0rked beyond repair by any means other than reinstalling Windows. On a system with an ATX motherboard and ACPI BIOS, it will often kill the power to itself at this point, and you'll never even see the message!
I think this error usually comes up due to a corrupt Registry or a bad device driver.
The few times I've seen Windows 2000 BSOD with a STOP error, it actually displayed just what was wrong (hard disk read error, in that case). It seems to indicate that Microsoft put quite a bit of effort into making Windows 2000 a suitably reliable and robust operating system, unlike the 9x series and XP.