Breaking Down Your Computer
If you've never worked on a computer before, it can be a bit intimidating the first time. The following are the basic steps you should perform (we're assuming here that this is your first time performing an upgrade):
Label all the cables coming out of the back of your computer.
Label all the connectors to correspond to the attached cables.
Turn off the power.
Disconnect all cables plugged into your computer.
Move the system to an area where you can blow out the chassis. Remove the case cover and use a can of compressed air to thoroughly blow out the system.
Move the system to your prepared work area. You can move most systems with the cover off, but you must be very careful about bumping into things because all the delicate internal electronic components are exposed and unprotected. Replace the cover before moving the system if you are uneasy about this.
Finding the Right Jack -
As long as you're labeling things, here's a hot tip: The sound card on your system has several mini-plug connectorsone for your speakers, one for a microphone, and probably a line in and a line out. They might or might not be marked with cryptic icons or actual words etched in the shiny metal of the bracket end of the peripheral card, and these might be readable (in a strong light, with a magnifying glass, up on your work table). However, after you install the system and you have a handful of cables snaking this way and that, chances are good you'll be unable to read these default labels. Save yourself some headaches down the road and mark the back of your chassis (or the top or the side) and pencil in which connector is which. Then, when you're trying to plug in a microphone or headset, you'll know that the first plug on the left is the speaker, the second is the line in, the third is the microphone, and so on.
You're now ready to work on your upgrade. You should have a clean, uncluttered work area with adequate light and ventilation. When your upgrade is complete, replace the system and plug all the cables back in.