"Antivirus System Pro alert" keeps popping up...

The antivirus sytem pro alert keeps popping up in the bottom right of my computer. Also a Windows Security alert balloon keeps popping up. it appears to be a fake, because the icon in the top left of the popup is a distorted looking red circle with an X, like its trying to imitate windowas...also, it contains a typo!! Anyway, I also get a box that pops up in the middle of my screen that says spyware alert..... AND, I would imagine these are related, but I get the internet browser coming on and loading a porno.org window, followed by a viagra window, and they just seem to keep multiplying.....HELP..... I ran the AVG free antivirus stuff, but the problem keeps coming back.... this is soooo frustrating....

Thanks for any help you can offer

Please download the current version of HijackThis from HERE

• Double click and run the installer.
  
• It will install to C:\Program Files\Trend Micro\HijackThis\hijackthis.exe
  
• After installing, you should get the user agreement, press accept and Hijack This will run.
  
• Select Do a system scan and save a log file. This will open a notepad file of everything Hijack This found, copy and paste it back here.