Hey,
I downloaded Natural-selection 3.0 client and installed it; I downloaded Natural-selection 3.0 b4 patch and installed it; I downloaded Natural-selection 3.0 b4a patch and installed it. I opened steam, and on my "Play games" list there is no Natural-selection. Im not sure what I did wrong, maybe i installed the files into the wrong directory. If you could tell me where I went wrong that would be greatly appreciated.

thanks,
sketch

C:\Program Files\Steam\Steamapps\accountname\half-life\nsp
That's the default folder. If it's anywhere else, try Steam\Steamapps\accountname\half-life\nsp, with Steam being the Steam folder. There should only be one nsp folder and it should be in this place. If it's not, move it. If there are 2, delete and reinstall.

If that folder is there, try restarting steam. If that doesn't work, go for a reinstall.