KillrAce

Well, my problem began when I tried to start some program I downloaded. It never came up, but it acted like it was loading something for a minute or so. After that, I continued browsing the internet. 10 minutes later, my browser shut and the computer rebooted by itself. When I tried to re-enter safe mode w/ networking, it came up but when I signed in it took longer and some chk.exe or something error popped up. Once it finally booted, the start menu was inaccessable. I tried opening Internet Explorer 7, but it flashed and closed. When that happened, the start menu came up, so I accessed Firefox, but it acted as though it was disconnected from the internet, but it wasn't. Also, my My Computer Icon disappeared. I figure it's a virus from the program I downloaded, but I can't download AVG to check because I don't have another computer to do so. I'm typing this through my psp which has no problem accessing this internet connection.

Edit: Also, there's nothing inside the Network Connections folder or the User Account folder.