If you can atleast Run Half Life 2 you can run it.
Any Source GamePreferably CS:S as most gmod users have this
umm ok this doesnt make this much since, if your asking if gmod damages your computer, it depends on which gmod you have (if you got it free its gmod 9, if you got it for $10-13 its gmod 10/11). in gmod 9 there were LUA viruses, in gmod 10 there are fake addon viruses so you should just scan for viruses when you download addons (www.garrysmod.org). if you play online there are some players who find it enjoying to spam props and nukes until you crash. also if your computer is lower-end then some of the maps and addons can crash it. but OVERALL no, garrys mod does not damage your computer, some addons and players do. just be careful which addons you download. if your just playing gmod to build contraptions, probably no dammage there. OK now if your asking about some sort of computer in gmod (PCmod?) that damages players or something like that try www.facepunch.com/index.php
Gmod is only for the computer. You just install Steam (you can install it buy going to Steam.com) and then there you have it. But you will need a source, so will need to buy either Tam Fortress 2 or Half-Life. Gmod is also 10$.
No, you do not need to be on the game you bought with Gmod to play it although you do need to have the game installed to run gmod and i also recommend having the game Half-Life 2 installed to get most of the textures and weapons and npcs and props that go along with it.
Worst? Commodore 64.
Yes
They have a benchmarking tool you can run that will tell you if you are able to run it.
No, the Air can not run GMod because it doesn't have a level 9 graphics card.
no. gmod is only for the pc.
No. Gmod is only for PC
You need to download Gmod 9.0.4c when you start there will be 3 choose unmark the Gmod 9.0.4b and your set to go and play gmod 9 online.
When you are at the steam store you can select the game and it will tell you its size.