I am just throwing this idea out there. It might be obvious to everyone but I just want to open a discussion on the subject.
I acquired a promo copy of Photoshop Element 8 recently. So it is a few version behind. It came with my Wacom pen tablet.
So here's my bird brain idea. Since it came with a valid serial number. I was thinking of buying the PSE 10 upgrade version.
Do you think it will allow me to upgrade my promo version into the latest PSE10?
The second part is. If it did not allow me to upgrade. Could I return the upgrade version and buy(upgrade) to full version instead? I'm afraid to get stuck with an upgrade version that I cannot use.
I guess I should be putting the question to Adobe more than anyone else 
I like saving $$$
