Elysian Shadows

So I'm doing Let's Plays and all on youtube, and I don't have a really good mic, in fact it was part of my $80 or so headset so its not the best.
My problem is that I have a loud hiss in the sound from my mic (the boost im assuming) and if I try to lower the boost through my computers recording devices it seems to just reset itself back to +20 after a while. I tried splitting the audio from the video, doing a noise reduction filter in audacity, and then putting it back on the video but that makes the voice quality kind of choppy and messes with the game audio pretty badly. I'm hopefully saving up to get a better mic soon, but for now that is out of the options. If anyone could help that would be great. Thanks.

apart from the obvious things you already tried.
i had a similar problem when i had a fan blowing near the computer. even though it wasnt very load, some reason the sounds used to catch well in the mic.

I was experimenting with the length of the noise reduction samples, and I think that will really make a difference. A long sample will reduce all noise but really almost get rid of the games background music, but with a shorter sample, everything is more clear and there is still minimal noise. I think I'll do this from now on until I get a better mic because the difference in the sound quality is crazy. If you want to hear how much it changes just look at my most recent youtube video compared to the last ones. (http://youtube.com/girandsamich)

also depends on what you use as a noise reduction sample.
If you reccord about half a minute without any game music in the backgound and without anyone speaking, just the hiss of the mic port, then using it as a reduction sample it should not get rid of the game bg music coz it really isnt in the sample. using a sample really reduces what is similar to the sample in your recording and nothing else (e.g. background music or msn notification sounds etc).
Use a noise reduction sample only of what you want to be quiet in the product and not any random selection on your audio timeline^^

I know this sounds like it wouldn't make a huge difference, but I actually go to a film high school and this is our method (sure our sound mats are professional, but) if you use thick blankets toward any direction that sound bounces really well, it increases sound quality about 10 fold. We box our interviewees and sound recorders in a small sound room and cover the walls with thick blanket like mats, and even when using the shit microphones. It makes a big difference. Let me know if it helps, it might not with your mic, like it does with our sound recording mics at school. But if it works, cool, if not sorry.