Hi
I note from the other thread regarding audio interfaces that you are on a bit if a budget and you didn't want to buy an interface if it could be avoided?
Btw, I know what you mean about recording guitar direct - just not the same, much better to mic an amp.
Anyway, the answer might be to buy a USB microphone. I've never used one, but, as far as know, they just plug straight into a USB port.
Also, you will need a DAW (software) to use to record, edit and mix (ie apply effects etc). There is an excellent one available online called Reaper. It's cheap to buy and can be demo'd for ages.
One caveat about recording with mics using a computer - mics can be very sensitive and if your computer makes alot of noise with its hard drive or fan then the mic will pick this up and spoil the recording! I use a laptop and I have had to resort to putting it outside the room when I record!
(Sorry if you know all this already!)
Hope this helps
Oops - forgot to say - When I first got into recording about 3 years ago I found the fllowing website which has a really good basic guide to recording:
http://www.tweakheadz.com/guide.htm