If you would like to play your electric guitar through your PC speakers, you can as long as you have the appropriate adaptor. Standard electric guitars and amps use cords with quarter-inch jacks, whereas PC speakers use cords with eighth-inch jacks. You will need to obtain one of two types of jack adaptors to play your guitar through your PC speakers: if your PC speakers can plug directly into an electrical socket, you will need an eighth-inch to quarter-inch jack adaptor; if your speakers need to be plugged into your computer to get power, you will need a quarter-inch to eighth-inch jack adaptor. These adaptors can be obtained at most electronics stores and some music stores. Also, you can find several options to purchase through the link in the Resources.
Apply the eighth-inch to quarter-inch jack adaptor to the male end of the cord that would normally run from your PC speakers to the back of your computer.
Plug the adapted quarter-inch end of the PC speaker cord into your guitar.
Plug your PC speakers into a wall outlet, turn them on and begin playing your guitar.
Turn on your computer with your PC speakers plugged in as you normally would.
Plug one end of your guitar cord into your electric guitar and apply the quarter-inch to eighth-inch adaptor to the other end of the cord.
Plug the adapted end of the guitar cord into the eighth-inch jack labelled with a microphone symbol that you will find on the back of your computer near where your speakers are plugged in.
Open your computer's Start menu, then click "All Programs --> Accessories --> Sound Recorder".
Begin recording a sound with the Sound Recorder program and play your guitar. You should hear what you play coming through your PC speakers.