Windows Account

Okay. I seem like a real dumbass, and I probably am. I was downloading American Pie 2 from Kazaa(I know I know..). It seemed okay, and it was a reliable user. It finished, and it asked to install a viewer. It was an .avi and I doubt it was a virus simply because it had be download a viewer. I downloaded the viewer, and restarted. My Windows login screen came up. My name was there, and I hit enter like usual(no password). It took me to the default windows account(nothing on it..barren 600x480 res...etc). I was like, "Oh, musta hit cancel accidentally" I restarted and hit enter. Same thing. Tried everything. All my passwords, all my accounts..no luck. I went into User in Control Panel, and made a duplicate of the other profile. It went through the steps, and came up with an error at the end. I fixed up my settings, and made my computer usable. Downloaded PC-Cillin and ran it through for a virus. Nothing came up, and my files are still intact as they were scanned in the process. I know they're there, I just can't login to my Windows Account. I'm pretty sure at this point that I don't have a virus or Trojan Horse, it's just windows being messed up. Plese help me, someone. I have no idea what to do. My friend said that if I hit 'esc' at the login screen, it would take me back to how it was..but it didn't work. I'm really scared now, because I have a ton of files and programs I can't lose. Ahh...I'm scared!