How to erase this virus?

Hi,
Yesterday a friend of mine came to my place to drop him some music files into his usb. But into his usb, there were some other files, that he wasn’t able to recognise himself!
My pc started lagging, and therefore I was forced to do a reset.
When it opened, I formatted the usb just to be sure that no virus is on it, and then disaster started.
First of all, the antivirus starts and closes immediately. I’ve runned trojan remover 3 times , removed what was found but nothing… The virus is still here… And what do I mean? Internet Explorer windows pop-up every once in a while getting me into strange chinese sites.
In addition I can’t download many things from rapidshare (… when I press download firefox closes)! WinRar opens whatever it wants!
I’ve runned Eset Online Virusscan, and it found 10 viruses. I’ve made even a system recovery, but still nothing..
I have 2 hdds, and therefore if I must format them, I will lose all the important personal files of my.
So what to do? Back the files and format the hdds? Try another magical antivirus? or just get my pc done in a technician and get me ripped off?
Thanks for the instant response. I’m currently running MalwareByte’s Anti-Malware and then I will use the other software you recommended. I was surprised to see that it was successfully installed as I thought there was some kind of banlist to the files used 😛

If you have to reformat you only have to do the hard drive with your OS on it. Viruses don’t attack data. I have two HDs and four partitions on my desktop: one for XP, one for Vista, one saved for Win7, and one for data. If/when I get malware that causes too much damage to repair I just reformat the infected partition and everything else is safe. But I still backup to another PC and DVDs frequently in case the second hd crashes.