where can i get the code for my stock stereo ('00 prelude) i changed it for a new head unit but a friend wants to buy mine and i dont know the code

 

Try looking behind the fuse box cover. Maybe it has a sticker with that info there.

 

If you have the factory radio out of the car you can get the serial number off of it and can call a honda dealership. If it is in the car try turning the radio off pressing presets 1 and 6 then turn the radio on it may show you 2 sets of 4 numbers write them numbers down and then call the dealership.