The "other" problem with that MBPro6,1 is that it came with a special build of Snow Leopard. If you try the commercial Snow Leopard that you can buy from the Apple web store, you will find that you can't boot the MacBookPro, even though the Snow Leopard version appears correct. The hardware is just enough different that you can only boot to the installer DVD that came with that MBPro originally. Apple never updated the standard installer for Snow Leopard to include those in-between models.
There's work-arounds, of course, but it's one area that makes it much simpler to just move on to newer OS X versions, particularly if you no longer have that original installer DVD.
There's work-arounds, of course, but it's one area that makes it much simpler to just move on to newer OS X versions, particularly if you no longer have that original installer DVD.