Depends on the new CPU and current motherboard, and assuming you are only changing the CPU. Upgrading to another bulldozer, like 6100 with the same architecture, probably no problem. Upgrading to the new piledriver like 8320 you may need to update the motherboard BIOS, but that is unrelated to windows. Chances are after the upgrade, or after finding out it's not needed, you will still have minimal changes if any since they are still very similar.
Would need to look up your exact motherboard model and bios so see if it supports piledrive already.
And of course if you are going intel, you'll need a new board, and at that point is best to reinstall from scratch.