Basically the difference is with Upgrade you must have an existing license for a Windows OS. Since you have XP then you are good to go. The downside is if you have to reinstall it is a little more difficult. Especially if you want to move it to another PC. You can do "clean" install (format your machine and then install through custom install) but takes a few tricks.

Full install doesn’t require an existing O/S but it will let a person upgrade from Vista to Windows 7. There is no direct XP upgrade regardless of the edition you buy.

Here’s a breakdown of the different editions of Windows 7 comparing the features: http://www.microsoft.com/windows/windows-7/compare/default.aspx

And here’s a helpful page explaining your Upgrade path options and some FAQs: http://www.microsoft.com/windows/windows-7/get/upgrade-considerations.aspx

Cheers,

Walker
Windows Outreach Team

You can purchase a Windows 7 upgrade for your machine- this will work with XP and Vista, the installation builds on the previous Windows System. The full version is for those who do not have a recent version of Windows. I do recommend you use the Upgrade Advisor before purchasing your OS- some older machines may not fit the system requirements or have drivers available for upgrade, though a majority of them upgrade easily. You can find the upgrade advisor as a part of this step-by-step upgrade guide: http://windows.microsoft.com/en-us/windows7/help/upgrading-from-windows-xp-to-windows-7.

Cheers,
Tara
Windows Outreach Team

Win 7 ultimate is a great choice as include many other amerinies Win 7 Home or Pro doesnt have

RICK