bizarre pc problem that i cant get to the bottom of.......

[hellrot_e34]

a couple of weeks ago my pc started acting very strangely.... firstly the wallpaper had vanished along with a lot of the desktop icons but not all of them, when you try and access the hard drive via c or my documents is says that access is denied and acts like nothing is there suggesting everything is deleted but when you do a search it finds everything that was there before, certain programmes dont work properly including msn messenger, when you click on it nothing happens at all, also virgin online poker and world of war craft refuse to connect. i assumed it was spyware or a virus and have run various scans with spybot and avast antivirus etc but they found nothing, has anyone got any idea what the hell is going on and how to sort it!!??