Microsoft veteran's worst Windows bug was all about Pinball
Pinball shipped with a frame-rate bug that rendered frames as fast as possible, causing extreme CPU usage until a frame limiter reduced frame rate and CPU use.
Microsoft probing why Classic Outlook is so CPU-hungry
The issue can be observed by opening Task Manager and watching the CPU usage rise. Microsoft offered little in the way of a fix, saying only that 'the Outlook Team is investigating this issue.'