How can I connect my Guitar to the Computer?

If your amp has a 'line out', use that instead of the headphones port and connect that to your PC/sound card's 'line in'. This is, more or less, how you would connect an amplifier to a mixer. This time the PC and the audio software you're using is the mixer/recorder/every thing in between. Set the amp's output volume just high enough before any distortion or clipping occurs. Do all other adjustments from volume to effects on the software.

Generally, it all depends on whether the electric guitar that you want to use through the computer is MIDI compatible. If it is, you need a special card that goes into your PC, and converts the sound into a digital signal, and then some software to convert it back into sound through the PC. You’re not going to have any luck just by using that cord you spoke of. When you attempt to plug your guitar directly into the computer your not really doing anything, there has to be something in between to process the signal that the guitar sends and turn it into something the computer can understand. This would be an external sound card. You're going to have to pick some kind of external audio device (sound card) for your particular computer. You can find an external sound card for pretty cheap these days. You might try inquiring about this at any local music store, or shop online at EBay. Once you have the external sound card just hook it up to the computer (usually USB or firewire) you can then configure it by following the instructions and plug it into your guitar in. Good Luck!