UPDATE:
Just phoned me sister to see how she is getting on.
They left windows installing over night and was loaded by the time they got up, seemed it hadnt stalled but was behaving liike defrag does at 10%.
Anyway, the computer was still acting funny, so they did the safe mode reboot and managed to run spybot, which found a lot of reg key changes.
Seems the initial freeze was due to a trojan download.
They cleared those and all is back to factory settings.
Thanks for the help and advice guys..
