[how to use your computer as a handy guitarist's tool]
The computer can help you as a guitarist in lots of ways. The only thing to do is plug your guitar in the "Mic In" of you sound card and - boom - suddenly the coolest effects are possible without you having to buy anything. Not even speaking of tuning your guitar.
But even if you don't want to plug your guitar to the computer you still have several more things to try. You can compose songs, create tablature from a .MIDI-File or have computer do it for you just by providing a .WAV-file. Be sure to check out the Guitar Online Software Suite which combines these features.