Choosing the Right Version of Windows 7

"One of the most frequent questions I get these days comes from people who’ve been running the Windows 7 beta and RC and are planning to upgrade to the final version when it’s available on October 22. “Which edition of Windows 7 do I need?” Interestingly, this question also comes up in other contexts as well. When Apple defenders appear in the TalkBack section here, they regularly insist that the Home Premium edition is “crippled” and “stripped-down.” Sooner or later, they insist, any self-respecting Windows user will have to upgrade. Based on that argument, they say that you must use the more expensive Ultimate edition to compare the costs of a Windows PC to those of a Mac, which comes in only a single edition. As you’ll see from the table below, this isn’t accurate."

Check out the linked article for the full table comparing the versions.  The short version is, that Home Premium is a very comprehensive product and will suit 99.9% of users just fine.  The additional features in the upgraded version are pretty specialized and if you need something more, it will be pretty obvious to you when you look at the list.