Many thanks, that's got it up and running.
Will I need to modify the registry to stop it happening the next time the machine is booted? If so, which key is it?
The client version was 4.7.1005.0, I'm not 100% sure a scan was running but it was difficult to tell what the machine was doing, it was certainly thrashing the HDD for a good 10 minutes before we gave up on that route.
Thanks again.