Need help getting addons to work

Hello, I am new. I recently purchased gmod from steam, along with HL2, HL2 Deathmatch, and Lost Coast. I know where to put the addons, but when I start the game, they don’t show up, except for one that did work.

The addons (with links to them) I am having trouble putting in gmod are:

Quarians and Geth - http://www.garrysmod.org/downloads/?a=view&id=93623

Tali’Zorah.zip - http://www.garrysmod.org/downloads/?a=view&id=93159

Enhanced Citizens V2 - http://www.garrysmod.org/downloads/?a=view&id=115471

The mod that did work:

Sonic The Hedgehog Mod 2009 - http://www.garrysmod.org/downloads/?a=view&id=58385

EDIT: Computer specs

Operating System: Windows 7 Home Premium
Processor: Pentium® Dual Core CPU E5300 @ 2.60GHz
Installed Meomory (RAM): 6.00 GB