While Windows XP came out I heard about a testing feature that existed to manually cause a BSOD (Blue Screen Of Death). I also heard this was supposed to be removed in XP Service Pack 2. It didn't get removed, it's also in Vista and Windows 7. To Enable this navigate to this location in the registry:
CrashOnCtrlScroll as a
REG_DWORD with the value of 1.
Now reboot and Press Ctrl+Scroll Lock+Scroll Lock, and you get a BSOD.
Why is this feature still here?