In their infinite wisdom, the IE team thinks it’s a good idea to differentiate the versions of IE7 for XP and for Vista. It is a valid concern to have; especially for support calls. But, since they run on different operating systems, they needed yet another modifier in a product name, because saying you run Vista or XP is much more difficult. So, here you have it: IE7+ is IE7 for Vista and IE7 is IE7 on XP. I would have just left it as IE7 on Vista and IE7 on XP, but I guess the + makes much more sense.