Downgrading Mac OS, is it possible to deactivate Adobe?

Hi! I'm a Uni student and recently bought the Student version of CS5 Design Premium.

I upgraded my Mac last Summer to the new OS X Lion - to be honest, it's a loada rubbish - it's made the laptop a lot slower and to be honest, I don't like it at all.

I was just wondering though, if I downgrade to OS X Snow Leopard, everything will be wiped, including CS5 Design Premium. When I bought it, it came with two serial keys - I've only used one, yet if I do this downgrade, I don't want to have to use the second and last serial key.

Is there anyway I can somehow like deactivate the serial key and re-use it, so I still have one free - and am not using the last one?

Cheers!