my guess would be Audacity, and one of those adaptors from your amp (if you have a solid state with that opion on it). if it doesn't have a recording jack on your amp... microphone would do it. and like Telecaster7 said, you'll have to spend a few bucks on the microphone for good sound quality.

and sorry TS, that was somewhat rude of me. i gues i was trying to say that you may get more dialog if you use the Search box first, get a couple of ideas, and then come back here and ask for advice 'cause there are several ways to accomplish your goal. Riff and Recordings forum, as mentioned, has a ton of information and this topic comes up about every day.

Some options include:

x$$ microphone plugged into PC, with maybe a better sound card don't know, and them 'mike' your amp as you play.

cheap multi effect pedal that has USB - then USB to PC. no amp

line out from amp into PC - not as familiar with this so be careful as my guess would be that it depends.

Lightsnake or Stealth plug...has built in sound card for codec and is guitar strait to PC

other options too

yes Audacity.net is free and legal and does a good basic job for PC software. i use it.

hope that helps