Texture problems

ok so i started it up and it ran fine but when i got into a single player game i was like wtf!! the ground is all weird colored and when i kill npc’s it crashes and i tryed using adv dupe with txt files and it just looks like a big box of errors… also explosions crash the game with looping audio =/ ive tried dxlevel ive also reinstalled garrys mod , i bought the pack with counterstrike source and Cs works just fine it might be my drivers but i dont have much money to work with so if there are any suggestions i would really appreciate it EDIT: also some textures on some things are purple and black checkered boxes

The purple and black checkered boxes just means that those textures are missing, but I’m not sure what yuor actuall problem could be. My first guess would be Ep2 and Ep1 not installed, but I’m not sure if your playing on maps with those textures. Now, the Npc’s, I can’t explain.