So you need older drivers for no CPU bug, you need newer drivers for 7GPU support, so Linux is the only one that can do both

If it works under Linux I don't see why you don't want to go that route: Linuxcoin for example can even run on a USB stick which saves some power from the hard disk you're not using as a bonus.

If you want to stay Windows:
Make sure to really clean the drivers before installing new ones, this is not just a suggestion made by AMD, it's really what should be done.