You can pack your computer as a checked bag, Mark Mayo's answer covers how to do so pretty well.
But I would highly recommend against packing a desktop computer. With all the wires and whatnot it will look "suspicious" to security personnel, and they'll almost certainly go through your bag (likely not repacking it with any care).
I would recommend shipping the computer to the destination, even a service as simple as the postal system. It will undoubtedly take longer to arrive, but if properly packed will arrive in tact.
I've worked with computers for half of my life. Shipping has never failed me yet. Overzealous security personnel, well I've got a few stories about them already...