How to clean this: Trojan Horse -- C:\WINDOWS\system32\mscmsr.dl

How to clean this: Trojan Horse -- C:\WINDOWS\system32\mscmsr.dll

please provide your suggestions. thanks.


details:

Scan type: Realtime Protection Scan
Event: Virus Found!
Virus name: Trojan Horse
File: C:\WINDOWS\system32\mscmsr.dll
Location: C:\WINDOWS\system32
Computer: myComputer
User: SYSTEM
Action taken: Delete failed : Quarantine failed : Access denied
Date found: Friday, July 10, 2008 5:33:51 AM