Trojan Horses

Hi folks. Can anyone assist with advice. I recently got a couple of Trojan horse viruses on my PC. AVG free picked them up but couldn't remove or repair. At least one was a "key stroke logger"  not sure about others.  At the time i didn't have anything of importance on my hard drive and it was very small anyway(40G) so i just binned it and bought a new one. Fitted it and loaded Win XP and other software and comps been going great.  I am worried as someone i spoke to told me (not an expert) that it might be possible the virus could still be in the PC as it could have "hid" in the motherboard cache. Is this possible? I run AVG scans frequently and all seems fine  but as i use comp for internet banking I'm a bit concerned. Any advice would be greatly appreciated.
 THX

http://www.computerhope.com/forum/index.php/topic,46313.0.html

go to above and complete , post the 3 logs here , an expert will see them