I have Win32:CTX please help

Avast 4.1 reports that I have Win32:CTX, but gives me a “Access Denied” message in regard to the file "imscan.dll [UPX]. I guess that means it’s the only file infected(?) But I can’t even delete it in safe mode. What do I do?

can you scan with a DOS scanner or just delete the file manually in DOS?