Okay, click properties in that window for that particular device. Click the Custom Tab and check the box for the +20 dB gain. Under the Levels tab, make sure you're at 100%.

We may actually be through the thick of things at this point. Turn off all applications that are causing sound through your speakers. Then, turn up your speakers a bit. Tap/talk and see if you get any sound through the speakers that indicates this is going on. While doing this, watch your little green bars and make sure they are getting near the top of that (just to guarantee the mic didn't inadvertantly mute or something). If it works, we're done. If not, we move on.

Next, we need to figure out what software came with your sound card. This could be a difficult thing for me to reverse engineer. I'm working with Creative stuff on my end, but let me see what I can come up with for you. My big problem is that I can find nothing about the sound card on the website or any other source. So, we move on to different methods.

In your control panel under the sound category, are there any other options that seem like third-party software? If not, look through your start menu and see if there is anything like "Realtek HD Audio Manager" or something like that. If not, do a search for it. Safest bet is that you have a Realtek sound driver.

If you can find it, you should be able to find an option to unmute your microphone in there. Then you can test again, and you should be able to get some kind of sound through your speakers from your microphone in real-time. After that, you can try the guitar, and it should work immediately.

Good luck. Let me know how it goes.