On my wife's computer there are two userids, hers and mine. Hers works fine (so far) but mine exhibits (what to me is) very bizarre behavior. A while back I was going through my email online and everything was pretty ordinary. All of a sudden, the screen blinked and my desktop icons turned to something that looked familiar but wrong. It turns out that with few exceptions every app icon invoked WordPad on some unreadable text file but not the same one. Also, some icons were unaffected. Things like "My Computer", the Recycle Bin, several folder shortcuts and some PDF shortcuts, and desktop.ini all retained their original appearance and behavior.
I managed to get rid of the false WordPad invocation by renaming it but that brought on the Explorer problem which is still with us. The unique aspect of this problem is Explorer never stops starting. It saturated two gigs of ram and the cpu now running at 100% and telling me about it every few minutes. Obviously, there is some sort of break appearing of I wouldn't be writing this. I found ways to invoke other programs by copying the target address from properties and pasting it in the "run" window obtained by pressing "Windows+R"-- keyboard shortcuts are very handy at times.
I've tried just about all the tricks I know except editing the registry. I hope somebody takes this ball and runs with it though I'm not optimistic. BTW, icons on the taskbar are not affected and work fine. The only message I get comes from a little house-shaped icon which only appears for the duration of the message. It says "High CPU usage warning. Click here for more information." If clicked, it opens something called "Resource Monitor", a probable HP Magic Canvas gadget.