Build and Learn
I needed to know that
Okay, building your own system doesn't save much money for the time it eats up. It's good you also get some knowledge out of the deal. Building your own system for the first time is all about the learning experience. The next time you build a system the time cost won't be as high, and building solely to save money will become a viable option. Knowing how to build a computer is a valuable skill. (Kiddies, you can make 10-15$/hr as a junior computer technician. Get a degree, add a few professional certifications and you'll start seeing the real money.)
Customized to your liking
What happens when you can't find a vendor that carries all the parts you want in your system? If the vendor is good, they can fill most requests, but don't expect to save anything on the requested parts. Vendors get discounts on high volume products, and they won't have those discounts on products they custom-order.
You could ask the vendor to build the system with the parts they do carry, and you can add any products they don't carry later. That works for easy to install components like sound cards or DVD drives, but components like motherboards and cases make this option more trouble than it's worth. You might as well build your own system at this point.
Building a computer with hand-picked components allows you to know your system inside and out. It'll be your own custom system instead of some bastard white-box machine. Everything from the motherboard and processor to the mouse pad will be exactly what you want. Additionally, the only corners cut those you cut yourself.
Who should build their own system?
If you only want to build your own system to save money, consider the time investment before starting. Is the 100$ saved worth the hassle? Of course, if you already know how to build a system, it won't be that much trouble. If you want to learn more about computers, you should definitely consider building your own system, but only try it if you're ready. Read through the rest of this guide to get an idea of the work involved in putting together a computer. Lastly, the only way to get a truly customized system is to build it yourself.