no mouse acceleration in paintshop or maya

uncheck start->settings->control panel->mouse->motion->'disable acceleration in games'

Function keys stopped working

Check to see if your keyboard has an F-Lock key. It's usually in the upper left or upper right area of the keyboard in the general area of the Function keys. Press it once, then try using the Function keys again.

http://jtsang.mvps.org/flock.html

Excel documents in seperate Excel windows

Tools|options|General tab|Ignore other applications (check it)