I was sorting a friend PC out, was absolutely riddled with Virus' and it had a process in the list called 'wuauclt.exe' which was appeared to be slowing things down, so I looked into it.

It appears that it is a file related to Windown Auto Update and is essentially not a harmful file. However, a virus called 'Cult Trojan' replaces this file with one an infected version of the same name, which drains system resources. There's alot of speculation on the Internet about it, with most people saying its just harmless and to do with Windows Update etc and missing the point that it is possible that an infected version of the file is possible!! I did read that the correct filesize is over 100kb, but since most of yours are 51.8kb, as is mine, as is the PC I fixed, I'd say either we all have it, or none of us do!! PMSL.

Thanks.