How do I get rid of a backdoor trojan?

The trojan is backdoor.generic2.YED and it always re-appears in my c drive as b.exe even after removing it with AVG. I have tried heaps of different spyware removers including: Adaware, Spyware doctor, Prev1x, and none seem to work. I have run Hijack this and below is a log of the scan. Thanks for all your suggestions and advice!

Logfile of HijackThis v1.99.1

Scan saved at 08:11:40, on 11/01/2007

Platform: Windows XP SP2 (WinNT 5.01.2600)

MSIE: Internet Explorer v7.00 (7.00.5730.0011)

Running processes:

C:\WINDOWS\System32\smss.exe

C:\WINDOWS\system32\csrss.exe

C:\WINDOWS\system32\winlogon.exe

C:\WINDOWS\system32\services.exe

C:\WINDOWS\system32\lsass.exe

C:\WINDOWS\system32\svchost.exe

C:\WINDOWS\system32\svchost.exe

C:\WINDOWS\System32\svchost.exe

C:\WINDOWS\system32\svchost.exe

C:\WINDOWS\system32\svchost.exe

c:\Program Files\Common Files\Symantec Shared\ccSetMgr.exe

c:\Program Files\Common Files\Symantec Shared\ccEvtMgr.exe

c:\Program Files\Common Files\Symantec Shared\ccProxy.exe

c:\Program Files\Common Files\Symantec Shared\SNDSrvc.exe

c:\Program Files\Common Files\Symantec Shared\SPBBC\SPBBCSvc.exe

C:\Program Files\Common Files\Symantec Shared\CCPD-LC\symlcsvc.exe

C:\WINDOWS\system32\spoolsv.exe

C:\Program Files\Google\Gmail Notifier\gnotify.exe

C:\Program Files\Synaptics\SynTP\SynTPEnh.exe