actually don't plug your guitar directly into your mic input. in layman terms: you will mess something up.
in musical "jargon" terms: a guitars output is Hi-Z which is has a higher impedance than the line level circuitry on your sound cards input can handle. You need either a DI box (direct injection) or a soundcard/interface that is designed for this type of thing.
hehe, you will mess something up AND what you record is going to sound like poo.
hope this helps.
BTW... I only go into so much detail explaining this stuff because I WISH this kind of information was given to me when I started making music...