Completely black weapons and patches of black on NPC's HELP!

Ok, so i bought Garry’s mod 11 about 3 years ago now, i bought the Counter-Strike: Source and Garry’s Mod pack. It worked fine for about a year, i updated it and everything, and then it had a problem with it. i left it a whole year uninstalled, then finally, just yesterday installed it again. During that year, i had my whole computer wiped, and upgraded to windows 7 (from Vista) and the problem still persists. What happens is, I launch Gmod absolutely fine, and i start a game and everything, it loads up, and its ok. But whenever i spawn an NPC, they all have black patches all over them. i figured out that somehow, these are patches of shadows. If i shine the flashlight on the NPC at a certain angle, they look normal. Same goes with weapons, if i use a different weapon, i.e Crossbow, it is completely black, so i have to get the flashlight, and point it in a certain place on the floor, for it to look normal, but then obviosly it just becomes black again when i move it away :frowning: This also happens with Counter Strike and Team Fortress 2. Any ideas? I will be greatful for any help i can get :smiley: