sounds like some sort of trojan/virus attack, goto click here and run an online scan of housecall.
other thing that springs to mind is the keyboard, some keyboards have extra function keys (shortcut keys to launch things like calculator/internet/OE or mail/screen saver/sound controls, and the normal music commands (skip/skip back/play/stop etc).
mine is a Genius wireless keyboard which does strange things when the batteries are running down (not what you describe but who knows)
if you have a multimedia keyboard with extra function keys the it might just be as simple as it being faulty OR maybe you need to install the drivers that came with the keyboard.
couple of things to start you off m8, good luck