My fraps doesn't record sound?

Hey guys, here's my problem, I open FRAPS and a game (mount and blade) in case you need to know. So i record myself playing and commentating, but when I playback to check it out, it comes out soundless! I checked my microphone using Realtek sound recorder and it works properly, so do the headphones, but when i use the program FRAPS it doesn't record anything! Please help because this is stalling my Youtube videos' progress.