I dident think it was... I haven't set up a miner using win 7, all of mine are linux hosts... My setup requires Dummy plugs, but I can't say what you need to do in your situation...

Some times my 7970 would start off running at about 1/2 speed but after about 30mins they are back up to full performance..

Sorry I cant help you further, I have always found google to be my best friend in times like this.

Good luck!