You never download loose dlls from the internet. Delete them. Gonna take a wild guess and say you probably have the unable to load import mss32.dll error, you probably haven't selected your correct mw3 folder. Click on game settings beside play on the launcher, and do that.
@Thomaskuhh It's saying page not found. Any tips? I'm trying to set this dedicated server thing up, and it's quite complicated. I'm not sure if it's simple and I just can't grasp the concept, or what, but it's seemingly too difficult for me.