I've had around 5 random BSOD on this machine since I re-installed Windows7 yesterday. Nothing harsh, just browsing the web. I also put together an old (5 years old) Asus P4 system the other day and had exactly the same BSOD 'Driver IRQL not less or equal - 0x000000D1'
I found that odd as I'd never experienced BSOD on either machine in the past!
I got thinking if new windows updates had anything to do with it!....Hmmmmm..
Many thanks for your help