What he said...Furthermore, I can recommend Avira - it's spot on with Win 7.
I've split one of my 500GB drives into three separate partitions, so XP, Fester and Win 7 have their own space and the MS Boot Manager has handled that without a hiccup. Linux is also floating about on a spare 160GB drive while I get to grips with Grub, so I can have a four-way boot option. I've retained XP purely for IL2 and one or two other games that Vista and Win 7 can't. Vista is a waste of time and I'll probably remove it at some point as I use Win 7 pretty much exclusively outside Tuesday, Thursday, Saturday and Sunday