Yes, it could overwrite any program, but (if I recall correctly) it hit OS file most of the time simply because they were always open. It was a very rare bug, b

Yes, it could overwrite any program, but (if I recall correctly) it hit OS file most of the time simply because they were always open. It was a very rare bug, because it had to combine both corruption of the VM to allow the write to happen, and a bug (e.g. a pointer error) that would write to the program's code page. The actual modification would usually be very small, and wouldn't change the file size. And yes, it was a serious bug, that might have been responsible for why Windows seemed to have a "half life". Over a given period of time, each system had a chance of corrupting itself. Some systems would be fine for years, but many needed to be reinstalled after a ~year.