Problem with PC running Vista, admin account not working (black screen)?

Right now I'm on the other account and it's working fine it seems, but the administrator account is completely dead except in safe mode when I can't do anything. When I log in the screen is just black, but it still automatically opens some kind of Vista security thing which is useless and when I close that out there is just this little dialogue box telling me something about Internet Explorer.

I'm not sure what happened, but I obviously messed up. Yesterday it started after I downloaded an mp3 off 4shared. All this **** kept popping up about how I suddenly have a million viruses so I ran a Full Scan with Windows Defender, but I don't think it worked, although it has in the past. I have the remains of non-working Norton and Protector Suite QL and Symantec all on here popping up all the time trying to get me to buy them and I ignored them thinking Windows Defender was just fine.

Now suddenly I have this thing called My PC Protector or My PC Security or something weird like that and I have no idea where it came from, but it's telling me I have 28 viruses while some weird Vista Internet Security (also mysteriously there) is telling me I have 41. I don't know what the **** is going on now.

So now I'm trying to download McAfee, which I can get free through my school (shoulda done that before, huh), but I can't do it without deleting all those other retarded dead antivirus things, which I can't do unless I'm on the admin account, which is dead.

So am i ****** and should I go to the Geek Squad or is this fixible for free?