also if you would like to expand your recording rig in the future, this is where to start. a usb mic will just need replaced.
+1. A USB mic is great if you want to invest $70 total into your pc recording. You're set to record 1 track at a time. If you want to upgrade in the futire you'll have to buy a real mic and an interface later.
tweakheadz home recording guide
is a cool resource to help you make up your mind where to spend your money.