Hi
nope, don't want to call you stupid
Use a negative LM7805, it's called a 7905, just turn things upside down.
If you want -5v from a 9v supply there are at least two ways that I know of, use a DC-DC converter or consider a charge pump IC, it all depends on how much current you need.
Additionally, if you have a centre-tapped transformer as part of your power supply - take the centre-tap to 0v and AC input to the the bridge rectifier, you will then have + and - supplies available for regulation
Hope this helps
Ed