Backdoor virus and trojan help

[ScreamingForVengeance]

Earlier today I downloaded an 11 gig torrent full of mods for a game I own. I should've went with my gut and stayed away from it because I didn't trust the site, but they were too tempting. Now, I don't use anti-virus programs, so I usually rely on your program to detect things because Malwarebytes is like the nuclear missile of virus detections. So I downloaded the file, and right after it was done I scanned the folder. It detected 3 BackdoorMSIL.PGen viruses inside it (which almsot made me crap my pants) then I ran a full scan and it detected a Trojan.Agent (which did make me crap my pants). Malwarebytes did remove all 4 of the viruses and currently they're sitting in the quarentine. I ran 2 more scans just to be safe and it didn't detect anything else. Now usually I would just be like lol gg hacker, but the backdoor viruses is whats making me uneasy due to their serious nature and how annoying it is to get rid of them. After I removed them, I had to restart my computer. After it restarted (this is after all my start up programs loaded), I started to notice odd spikes in my CPU usage and there would be slight lag when loading webpages. That only seemed to go on for maybe 5-8 minutes and after that it's been running normally. Since I didn't detect anything after the scans, do you think Malwarebytes managed to get rid of the viruses, or do I need to go into more extreme methods such as reinstalling Windows?

Also, the mod pack I downloaded came chalked full of multiple rar files for each mod. Since I detected and qurantined the backdoor viruses, do you think it'd be safe to unrar these files or should I just delete it off my computer and damn the folder to the forbidden zone?

[AdvancedSetup]

The safest bet would be to remove all of it.