Games wont work

[Maxwell637]

Ive just bought hl2 goty and it downloaded but when I look on steam it says preload complete and when I try to play it it pops up with the purchase screen.Someone help me please?

 

[PimpinPenguin]

I'm guessing you bought retail, if so have you registered your key with Steam? If you bought of Steam then try renaming the ClientRegistry file in your Steam folder.