Re: Software Upgrades for MS Office Pro 2010 - Win7 or XP
You don't need to run 64-bit Office on a 64-bit OS, 32-bit Office will run just fine on a 64-bit OS. Running 64-bit Office on 64-bit OS may give some performance gain or allow for larger spreadsheets or other files. You can actually install both the 32-bit and 64-bit Office on the same machine if running 64-bit OS.
Personally, I would stick with 32-bit Office unless I planned to create very large, compute intensive spreadsheets.
Unless you need to be able to log in to a Domain, Home Premium is all you need, no need to upgrade to Pro.