If I purchase an upgrade for Windows Vista (Home Premium) to Windows 7 (Home Premium), do I retain the key and download rights to Windows 7 in case I format my computer in the distant future? Ideally I would be able to reinstall Vista again and download Windows 7 to install at any time. It seems kind of silly to me if it's just a one time upgrade, but it can't hurt to ask. Any insight is appreciated, thank you.
according to the Windows 7 upgrade path you can upgrade anytime from Vista Home Premium to Windows 7 Home Premium or Ultimate.
Note: the upgrade path is only valid for retail versions of Windows. for OEM versions, refer to your vendors upgrade options.
although there is no 'official' limit to reinstallations, you may have to contact a Microsoft representative if they refuse activation, suspecting 'foul play'.
we all know about the 'full installation from upgrade disk' trick with Vista. if this option will be still available for Windows 7 can only be determined once the first Windows 7 upgrade media hit the shelves next month.
I am not sure you ever get "download rights", you will get a DVD that will entitle you to install Windows 7 over any edition of Windows Vista (or I think XP and a few others).
You can reinstall as many times as you like and if the key ever stops working, ring Microsoft, explain and they will either give you another one or unblock your current one.
On another note, have you checked the price of fully packaged product? I cannot comment about it for you as I can not see a location in your profile, but in the UK it is unbelievable that it is cheaper than an upgrade edition and so much better!