Guitarists and Bassists, please read!

I play bass. A few of my friends from work recently found out, and now want me to play it for them. Since it seems impractical to bring it anywhere, especially since I don’t see these people outside of work, what’s the best way to record onto my (Windows XP) computer? Like, are there any video cards or peripherals that allow you to plug a guitar or bass directly in to the computer, or do I need to use my microphone? Can anyone offer suggestions for software? Free is best, but not necessary…