Do you have a soundcard with multiple inputs? Or are you just relying on the mic input of your computer? I'm guessing the latter so, assuming that, be aware that quality won't be great just going straight into a mic input.
Anyway, you need a program that records audio to a file as it comes into the computer. There are lots of programs to do that but then they don't do much with the resulting file.
I'd recommend getting your hands on some multitracking software, then you'll be on the way to a home studio set-up of sorts, and you can start learning about overlaying, editing, effects etc. etc. Forgive me if you know all this already, just laying down the basics....
With the program installed, you'd plug your mic in and set up a channel to receive the audio, you should see things happening when you tap the mic (meaning level meters are showing activity on the screen), then you simply arm the channel to record and play away.
Doing it this way can present various problems, depending on the results you're after. For a start, you'll need to play around with the mic position if you're only using one so that you pick up the whole kit. Blah blah....
Well, let's not get
ahead of ourselves - you can always keep asking for help once you're set up.
Of course, you could just use Windows sound recorder to grab some audio using a mic. (Start > All Programs > Accessories > Entertainment > Sound Recorder). But then, presumably, you'll need to trim the file or edit it in some way. Then you could use an audio editor (e.g. Wavelab. Not free, I'll have a hunt for free versions - hold on.......)
Or you could do the lot in a multitracker. There is a free version of Pro Tools kicking around, but it doesn't work with Windows XP. I use Cubase SX3 but it's an expensive piece of kit.
It's no secret that software can be "obtained" from the net using p2p programs and clients like bittorrent, but of course I don't advise using these methods.
So here's some free software:
http://www.hitsquad.com/smm/programs/Audacity/ http://www.hitsquad.com/smm/programs/FatRockStudio/ http://www.hitsquad.com/smm/programs/KRISTAL/ http://www.hitsquad.com/smm/programs/LUNA/ http://www.hitsquad.com/smm/programs/QuartzStudio_Free/
All taken from
http://www.hitsquad.com/smm/win95/MULTITRACK_RECORDING/
I'm sure there are a lot more that others can recommend, this is just a start - there's so much out there.