Windows Vista Home Premium SP1 or SP2 -> Windows 7 Home Premium Windows Vista Business SP1 or SP2 -> Windows 7 Professional
Windows Vista Ultimate SP1 or SP2 -> Windows 7 Ultimate
If I understand your question, you are asking if the system is eligible to use the Upgrade package or will it need the Full package.
The answer is that yes, you can putchase the Win 7 Home Premium Upgrade package and upgrade your system from any earlier version of Windows.
That said, you should be aware that the Upgrade package allows both an inplace upgrade or a clean install upgrade from the Upgrade package. Which you use depends on your circumstances and in your case, I believe you will be required to do a clean install (what Microsoft calls a "Custom" install). An in-place upgrade migrates all your existing configurations, data and applications "in place" (although you are well advised to have a complete backup available). A clean install type of upgrade erases everything and does a fresh install of the Win 7 and you are then faced with the rather daunting task of reinstalling and reconfiguring 'everything' and then reintegrating your old data from your backup.
As I said, I believe you will be required to do the clean install (Custom) type of upgrade.