That's right, according to my understanding. You can upgrade from Vista HP to any identical or "higher" version of W7. But unless you're doing a like-to-like upgrade (eg: Vista HP to W7 HP) then it will have to be a full clean install.
I'm not sure about the student/teacher aspect though. I've no experience of this.
Make sure you have your Vista HP product key to hand when you do the installation.
Try running this click here I upgraded my laptop from Vista Home Premium to Win7 Ultimate without any problems (not a clean install). I only had to put in the Win7 serial number not the previous Vista one.
If ashdav successfully upgraded to a higher product without having to do a clean install, then maybe that's worth trying first. As he says, in that case you wouldn't need the old Vista product key, because the installer would detect your copy of Vista.
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