Nactor,
Basically what you need is something to translate analog to digital. Standard soundcards are primarily designed to run speakers. While they have a mic input, they aren't designed for simultaneous recording and monitoring. I learned this the hard way myself.
I think the easiest and inexpensive way to do this is to buy a USB interface like I suggested (but didn't explain) because they also have a built-in preamp which will make your mic sound better or work at all.
Standard soundcards don't have a preamp, so if you are even able to plug something into it, it'll sound like crap.
Here are a couple of ideas pretty much in order of price:
This has one port, so you can only record one track at a time, BUT you can still listen to your mix:
http://www.musiciansfriend.com/srs7/g=rec/search/detail/base_pid/703606/
Same with this one. In fact I just bought it, but I haven't played with it yet. Mine has two ports though:
http://www.musiciansfriend.com/srs7/g=rec/search/detail/base_pid/249700/
This one has two ports:
http://www.musiciansfriend.com/srs7/g=rec/search/detail/base_pid/701368/
This one has two ports plus it looks like you can do a few differnent things with it like adding hardware effects:
http://www.musiciansfriend.com/srs7/g=rec/search/detail/base_pid/245506/
You get the idea. Stick with brands like M-Audio, Edirol, Lexicon, and Motu. I threw in a Line 6 unit which is good, but they don't specialize in recording.
Remember that the more inputs a unit has, the more tracks you can record at the same time.
From here you can branch out, but with something like this you can get a good start.
By the way there are also similar units with Firewire that tend to cost more, and internal cards as well, but you usually need a seperate pre-amp with those, so USB can be a cheaper all-in-one type thing.
