What program allows me to do this? I am trying to make a walkthrough video and I do not want to have to go over 100+ hours of footage to voice them over. I would rather talk while I am playing. I've tried using xfire and it only allows me to record from one audio source at a time, I also tried Cam studio and FRAPS and they both only allow one audio source at a time. Is this even possible or do I have to go through the painful process of voicing them after I record them?

Record voice separatly in Audacity (or any other audio editing software you have) while you're playing and then import the audio into your video editing software with the game video.

Pro Tools allows you to record all of this, about about 30 other things of your choosing, at the same time depending on your setup, whether it's HD or not, etc.
However, Pro Tools is not remotely cheap.

I am not willing to pay for anything so I will probably not bother with this. Is there a free trial? For now I will try to use Audacity as suggested by Idon'tunderstand.

Use whatever free video recorder you want and use Audacity to record your mic. I've tried doing that, but it requires a little bit of a higher end computer depending on what you're doing because of all the writing/reading going on simultaneously.

My PC should be able to handle that. I never record longer than 10 minutes and I use the half size setting to make sure the file does not get too big.