If a shop reloaded windows on your computer, they should have activated it. If they put on windows 7 and you had no product key, they are in violation of Microsoft's COA and should probably be investigated. I run a computer shop and all the computers must have a key if we are to work on them.
I thought it seemed weird that it asked me to activate the product key. Then does that mean I should also just purchase an installation disk from a store or online that way I can be able to activate Microsoft properly, and if I do that will I lose the things I installed like photoshop or any of my files.