Garry's mod CS V.7a:
i will give the Gmod-cs V.7a(this mod using Counter strike Source):).
http://halflife2.filefront.com/file/CS_Source_Garrys_Mod_V7A;37945

For the upgrade
http://halflife2.filefront.com/file/CS_Source_Garrys_Mod_V7A_Menu_Extension;37958

to play Gmod-cs V.7a:
1.properties the CSS.exe shortcut in your desktop.
2.change "-game cstrike" into your gmod folder name(-game garrysmod-cs)
3.don't forgot to install gmod to the place you install CSS examp:C:\Users\user\Desktop\Counter strike source v1.7/garrysmod-cs.
4.enjoy
you can play gmod-cs V.7a with online.

Half life 2:
if you have problem in half life 2 while "start new game" because no:maps,sounds(VO for the scenes),and Scenes Folder,you must find this folder so you can play.

about the Half life 2 it's already installed while you install CSS.
to play the Half life 2,the .exe is in your CSS folder.

Steam:
steam mod I'm very like:http://www.fpsbanana.com/guis/23511

sorry if my english bad.