Map a share on a Win9x box to drive X: on an NT box.
At the NT command prompt, type
Crashes the Win9x box in 17 characters. In WinME they half-fixed it: the machine reports on a blue screen that the server service has crashed and offers to restart it. My suspicion is that the file name matches neither the pattern for the shortname or the longname, and so falls out the bottom of a test that was not designed to ever fail.
Of course that's all ancient history now, and I expect Google may actually fix the problem eventually, unlike Microsoft who ignored the bug report.