Also just to mention--if you do upgrade to v2010 (or any current version) you are entitled to use ANY prior version in its place. As John indicated, the thing you can't do is use a newer version (e.g., v2008) in place of an older version (v2006) without an upgrade. Consequently upgrades should usually be to the latest version (e.g., v2010) because then you can use anything you want (except v2012, v2014, etc.). Hope that made sense!