When I purchased the Win7 Update pack, it included the 32 bit and 64 bit discs. On my laptop I installed the 32 bit as that was what I had on there with Vista. Here's the dumb question: Would I be able to use the 64 bit disc on my desktop, which is running Vista 64 bit, or is the key good for only one or the other? I think I know the answer, but just making sure. Thanks.