Garry's mod not working, ocasionally crashes computer or firefox/chrome

So here is how it goes: Steam randomly uninstalled my Garry’s Mod. So I re install it, my laptop (windows 10 if you need to know) freezes up after launching it. Once it didn’t freeze up and it said "Failed To Read 3817212 bytes. I don’t know if this is piracy detection. No, I did not pirate the game, I legitimately bought it. I love this game and do not want to let go of it. If someone knows the solution to this, please reply to this post. I have not tested other games however I will after this is posted. Edit: I launched Team Fortress 2 successfully.

This suggests that either one of your mountable games or addons are corrupted.

Verify all mounted games, esp GMod, or delete the GarrysMod/garrysmod/cfg/mountdepots.txt and delete all .gma files in GarrysMod/garrysmod/addons/

Your title says that your game was crashing other programs.
You might want to take a look at this too

https://puu.sh/wRJ0z/2684d096f1.png

Thank you for the suggestion, I mounted Portal 2 and it had 6 files missing, that was the problem. My Garry’s Mod works now.