I'd like to thank everyone for what assistance they can provide. Norton Anti-Virus came up with the following files quarantined:
I don't know whether this fact matters but the original location of these files was c:/windows/system32.
I have been unable to remove the infected files with Norton. I downloaded VundoFix but it was unable to detect any damaged files. I've downloaded and run HijackThis and have included the log file as I do not know how to analyze it myself.
Again, any assistance would be greatly appreciated and if there is anything else that I can do to provide more information please let me know.