Windows includes a feature that you can use to cause the system to stop responding and to generate a memory dump file, We can use this to have some fun with your colleague.
This can be done so easily using just pressing 2 keys on your keyboard. But before that we need to create a DWORD key called CrashOnCtrlScroll and set the value to 1 in the below registry location.
If you have a USB keyboard:
HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\kbdhid\Parameters
for PS/2 Keyboard:
HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\i8042prt\Parameters
Now, reboot your computer and Press the following key to activate the blue screen death!!!
Right Ctrl + Scroll Lock + Scroll Lock
(hold down right Ctrl key and hit Scroll Lock twice)
Have fun!
More info about this feature:
Source: http://support.microsoft.com/kb/244139