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Assembly
2. Open and prepare the case
Most cases available allow access to the inside through their side panels. Some used to require you to take the entire sides and top off but since making your own custom computer is becoming more popular, the case manufacturers decided to make things easier. If your case doesn't come off in the described manner, just refer to the manual it comes with, or do some experimenting to find out how to open it up.
The following sets of pictures show two different cases illustrating how they can either come off in one piece, or have the side panels removed.
Removing the Case as a Whole
Removing a Case's Side Panels
Once the case is open, make sure you locate the power supply if it was supposed to come with one. If it already has a power supply, skip to the part of this step entitled " Installing the Risers. " Before you do that however, make sure your case comes with a bag of screws. These will be needed throughout the construction of your computer.
Installing the Power Supply:
Most power supplies are a standard size and should fit nicely in the case at the top. Just make sure the fan is unobstructed and the screw holes in the power supply line up with the screw holes in the case. It may help to lay the case on its side while screwing in the power supply. While your at it you may notice a small sliding red or orange switch that says 115v. This should remain at 115v if you live in the United States. After the power supply is secured, you should be ready to install the motherboard risers.
Locate the bag of screws that came with your case and take out the motherboard risers. They will either be plastic or metal. Either type will work, and in some cases you can use both. I prefer the metal risers because they usually result in a cleaner and easier installation of the motherboard. Right is an example of a typical metal riser.
You will need as many risers as there are holes in the motherboard. So carefully take your motherboard out of its anti-static bag and place it on that bag. Orient the motherboard as if you were going to place it in the case by making sure the connecting ports on the motherboard (where you connect the keyboard, mouse, USB components, etc) are facing out the back of the case. Count the holes in the motherboard and see where they line up on the inside of the case. It may be a good idea to mark these holes in the case with a highlighter or marker so it's easier to remember where to install the risers.
Next simply screw the risers into place, as seen above, making sure they're tight. If the motherboard happens to have some extra holes where there are no holes lining up with them in the case, just pop in some of the plastic risers with the pointy part of the riser pointing through the face of the motherboard. What this does is prevent the metal of the case from touching of the electronic components on the underside of the motherboard.
Once the risers are installed, you can get the front of the case ready for the drives.
Preparing the front of the case: 
When a case is brand new the front part where the drives will be are covered up usually by a metal piece as well as a plastic piece on the front that matches the case as seen to the right. First, decide where you will be putting your drive or drives. Typically a CD/DVD drive is put in the top slot of most computers, but it's completely up to you and is most often simply an aesthetic decision. The front cover for each CD/DVD bay can usually come off fairly easy with a flathead screwdriver. Once off, you may or may not have to remove a metal piece inside (as seen below). I'm starting to see where most cases don't even include the top metal piece since this is typically where most people put their CD/DVD drives.
Most likely this process won't have to carry over to the floppy drive since that is standard on most computers, but, if you have a ZIP drive then you may have to do the same thing you did with the CD bay, just on a smaller scale. Since ZIP drives are still popular, most cases include a bay just above or below the floppy drive bay. If not, then you'll have to get an adapter that will allow you to mount the ZIP drive in a CD/DVD bay. These can be purchased at TigerDirect.com .
Preparing the back of the case:
The last thing you need to do to prepare the case is make sure there are open slots to accommodate the motherboard's various ports as well as the ports that will be there when all the cards are installed.
Usually the motherboard comes with a rectangular metal piece that fits on the back of the case and allows access to all the necessary ports on the motherboard; ports such as the keyboard and mouse ports, and the USB ports. If the motherboard came with one, then replace the existing one on the case with that one. Make sure the round keyboard and mouse port holes are towards the top of the case, this will ensure they will line up correctly once you put the motherboard in.
Your case is ready!
Install the Motherboard (Step 3)