Can't mount certain games on Garry's Mod 13.

I have Valve Complete Pack and Garry’s Mod, with all the games already installed, and I recently re-installed Steam to fix a bunch of glitches, like Portal 2’s Co-op not working and stuff, and re-installed all my games and SDKs and Dedicated Servers, and… EVERYTHING, and I still can’t mount Counter-Strike: Source, Left 4 Dead, or some other games. I can mount “Counter-Strike: Source”, “Day of Defeat”, “Half-Life Deathmatch Source”, “Half-Life: Source”, or “Left 4 Dead”. And it won’t let me mount a mod called “Xeno Clash”. But it does let me mount “Age of Chivalry”, “D.I.P.R.I.P.”, “Dystopia”, “Half-Life 2”, “Half-Life 2: Deathmatch”, “Half-Life 2: Episode One”, “Half-Life 2: Episode Two”, “Half-Life 2: Lost Coast”, “Insurgency”, “Pirates, Vikings and Knights II”, “Portal”, “Team Fortress 2”, and “Zombie Panic! Source”. Can someone please help me figure out how to make other games compatible, including the listed games that shows a red X instead of a check-mark box, and also unlisted games like “Alien Swarm” and “Counter-Strike: Global Offensive” and other games that are supposed to be compatible with Gmod but isn’t for me due to glitches? I would appreciate the help a lot. Thanks. :smiley:

And please don’t make fun of my username. I am a genius, usually, but temporarily am weird nowadays, because I stopped taking these terrible medication that I’ve been taking for 12 years, which I never needed in the first place, and this medication withdrawal is a hard process, because my psychaitrists are all quack doctors, so I’m withdrawing from the meds the hard way, so I’m temporarily a screwed up “NOT-SO-SUPER-GENIUS” right now, so please don’t hurt my feelings, cuz people have made fun of this consistent username that I use on many websites, and it really hurts me, so please don’t make fun of me on this website, because I’ve been having a really hard life with adults disrespecting me and abusing me. I’ve been made fun of on the Black Mesa Forums and even on Kongregate already, and on some other websites. I just wanna get along and get help with these Garry’s Mod problems that I need help with really bad. Thanks again. :smiley:

And I have Windows 7, 10 gigs of RAM, a 1.5 terabyte hard drive, an AMD processor with 3.30 GHz, an i7 core, a Beats Audio sound card, an NVIDIA GeForce GT520 video card, and all of this is on an HP Pavilion HPE PC.