Worst Operating System Feature

From a Quora thread:

Windows 95 had a counter that added up every millisecond since the operating system was started. The counter would add up to 2^31 in a little less than 25 days, and the next millisecond, the operating system would crash due to overflow of the counter. In reality, however, that probably never happened, because Windows 95 could never run for almost 25 days without crashing for another reason.