But it still took you nearly a year to reply to this thread!

In reply to a post by gg11:

I installed a 775Ghz machine

Wow, better call AMD and Intel, they'll want to know who's making those chips!

Maybe, but I have only just encountered the problem

AVG is well known to cause computer slow downs. If you want a faster AV program, get a copy of Eset NOD32 or Eset Smart Security, which both use pre-compiled code which places a much lower loading on the CPU (and they're better than AVG at finding viruses too).