Spyware Detection Alert!/MalwareCrush help, it is stuck on PC!

Hi, thanks for looking
I have a problem with my PC, I don't have any idea how it got here although I think it was installed by a trojan that infected the PC.

My HijackThis logfile is:



I have searched the internet and it seems that this problem is fairly common, so I hope you guys can help me get rid of it. I tried one of the solutions somebody offered on another website, but it did not work. Something to do with SmitfraudFix.
The icon in my desktop tray is a small red ball with a white exclamation mark. When I click on it, it opens a window (titled Spyware Detection Alert) telling me I might be infected (how ironic) and when I close that window it opens a webpage where it 'scans' my PC (with MalwareCrush). Other users of the PC have told me that it accuses them of being on pornography websites. It is very frustrating.
I have used AVG Free and Spybot against it, neither worked. Please help!