Does your guitar happen to have a pick-up, or will you be mic'ing your instrument?
How good do you want your recording to sound? Is it just for messing around,
or do you want some decent sound quality?
I find the analog laptop input are fairly noisy and don't offer the best
representation of the original sound. If you're looking for more than
just an off the floor scratch of your playing, I would suggest getting a
USB/Firewire guitar box of some sort. There are many to choose from
and you can do a search in the hardware forum to get details.
Toneport/Line 6 is a pretty good brand of equipment for the money.