I don't really know what it finally was, as I did everything you suggested and that I could think of: off the mouse acceleration (seemed to help a bit, and System Tray is called Control Panel in PC), uninstalled/reinstalled the mouse, forgot to buy batteries for my another mouse, so I couldn't try that, and just now did the sticky keys-off thing... feels better and no double windows... I still need to check if PSP tools got fixed w/ this too...

Anyway, thanks for the help!

PS: While I was adjusting Mouse properties, I couldn't find how to fix the double click speed? Or do I just remember it from Mac? (I used a Power Mac 6200(?) for sometime two years ago...)