Library problem.

[MythlyInari]

So I tried to opt into Steam Beta, couldnt get on. I had to reinstall Steam.
Its working fine now and all, but here's the real problem:
You see, I have ALL my games on a seperate drive. Steam isnt detecting them. only Beat Hazard Demo on my C drive. Can anyone tell me how to make Steam detect my games from my D drive WITHOUT having to reinstall every game?
Thank you.