Popping the lid of a PC for the first time can be pretty intimidating, but there's really no need for concern. There's nothing inside that will hurt you, other than sharp edges and those devilish solder points (fortunately much reduced in recent years with increased surface mounting of electrical components). There's also nothing inside that you're likely to damage, assuming that you take the few simple precautions detailed in this chapter.
Some PCsparticularly those from big-box storeshave seals that warn you that the warranty is void if they're broken. This isn't so much to protect them against your ham-handedness as it is to ensure that you have to come back to them and pay their price for upgrades. We advise people to break such seals if they need to, do their own upgrades, and fight it out later if they have a problem that should be covered under warranty.
We've never heard of anyone being refused warranty service because of a broken seal, but there's always a first time. If you have a sealed PC that is still under warranty, the decision is yours. Note that some individual components inside, such as hard disks, are a special case. Breaking the seal on a hard disk does actually destroy it and will without question void the warranty. And, unless you are qualified to do so, don't ever open up a power supply or CRT monitor. Dangerous voltages await you inside.
Those issues aside, feel free to open your PC and tinker with it as you see fit. Far from forbidding you to work on your own PC, most online computer vendors actually expect you to do your own upgrades and repairs. As a matter of fact, most of them will try very hard to talk you into doing your own warranty repairs so that they can avoid sending a technician to do them for you. The rest of this chapter explains the fundamentals you need to understand to start upgrading and repairing your PC.