[QUOTE=Typhon;48066]I figured it out!
The standalone version of Mednafen created some sort of log file that I noticed, and I opened it up, and it said something about an error: missing sega_101.bin. So I went to emuparadise and downloaded it, extracted it, and got the standalone version working.
Then I just copied sega_101.bin to my retroarch system folder, and all is working!
I was under the impression based on a video that I saw by Lord Monkus that I only needed sega_100a.bin (Japanese) and mpr-17933.bin (American and Euro), but it was the sega_101.bin file that I needed.
Thanks everyone for your help (especially GemaH), I appreciate it![/QUOTE]
Oh crap, I just went back and looked at the video and realized I only had the 100 bios file in there, my apologies for that.
Glad you got it sorted though.
I have updated my video now with an annotation correcting this.