Every program causes this in Windows.
Explorer.exe has performed an illegal operation and will be shut down immediately.
by MEarnhardtFan August 25, 2004
1 more definition
If you have windows, your probably experiancing it right now.
(Illegal Operation Popsup) "Hey, wtf? I was reading about how lame Bill Gates was!" (Illegal Operation: That's why this popped up dumbass.)
by DennisTehMenace March 30, 2003