Ok, I can now go through the menus. The sounds a little distorted, and some sounds repeat over and over again, even though they're not supposed to (Something about hearing "Access Denied." multiple times doesn't appeal to me)
The problem of not being able to play the levels still remains however. It goes to the loading screen, then 4 seconds later, crashes to desktop. I already installed the 1.1 patch on the DOS version of the game. I am using VDMSound on the MERCS.exe file.
Getting through the menu's is now fine, like I said. My question now is how to fix the sound (If possible), and how to get into the actual levels.