Thank you. I had already re-set the defaults and now I have cleaned the fans as well as i could without dismantling and the cpu is running 10 degrees cooler and all is fine so far.
I didn't flash the bios - partly because it was scary and partly because the version I have is the latest according to the Dell site.
Sujatha - I assume that you meant up-date the bios - or is it possible that the bios may be corrupt and it needs to be refreshed? Just in case I have to resort to that some time later!
