Originally I had PS 7, and an upgrade to CS3. More recently I purchased CS6. I received a discount on CS6 but ASAIK it wasn't an upgrade, but the full version.
My question is: can I now sell my previous versions (PS7 and the CS3 upgrade), or do I still need them to legally use CS6?
If you bought CS6 as a full version,then you have a separate license from 7 (the original) and CS3, the upgrade and can legally sell it. That is called "transfer of license."
You know you have a separate full license when you are not asked to provide the serial from CS3 during install or activation of CS6.
Here's how to do this so the person you sell it to can properly register the copy in their name.