Help! Nul Trojan problem

Scan type: Auto-Protect Scan
Event: Threat Found!
Threat: Trojan Horse
File: C:\WINDOWS\system32\nul
Location: C:\WINDOWS\system32
Action taken: Clean failed : Quarantine failed : Access denied
Date found: Wednesday, August 16, 2006 10:55:48 AM

I seemed to have got this trojan nul. The file does not show up after I have checked the option of no hidden folders and norton can not remove it. I've also ran Spy Doctor and other malware programs. I just cant get rid of this trojan. Can anyone help?

Thanks,
Joe