Follow up to the problem.

The only way of fixing it was to do a total re-install of Vista. Once that
was done and all the updates applied and applications re-installed the
machine runs without problems.

Obviously there was some sort of corruption somewhere but there was no
malware detected anywhere on the system. The only two items that may be
related was there were some dodgy MP3 played which may have automatically
downloaded a codec containing malware. Also the system was reporting traced
of having Norton installed and to my knowledge it had never been near the
system.

"Russell Jesson" wrote:

Vista Basic Machine started running very slowly and when I looked in Task
Manager svchost.exe was using a 100% CPU. Using system internals process
explorer it’s the network service containing crytsvc, dnscach, KtmRm, NlaSvc,
Tapisrv and Termservice.

Looking inside the thread that is using the CPU is ntdll.dll

I’ve ran all virus and spyware checkers I can and all show no problems. I’ve
booted in safe mode and cleared all the softwaredistribution folder. The slow
running does not affect safe mode but as the service is not started no great
surprise. Windows Update doesn't work in safe mode either, thanks Microsoft.

I tried to update AVG virus checker but it wanted KB929547 applied so I
downloaded it and tried to run but after several hours all I got was install
failed with 0x800706bb

Any ideas??