Newly built computer won't boot

It is not clear how experienced you are at buttembling these boxes. First load just a video card, hard drive, cd (or DVD) rom and 1 memory stick. Ensure everything and all cables are seated properly. Ensure the BIOS settings are set to optimal, that the hard drive is set with the correct jumper, plugged into the correct IDE or SATA port (ditto for your cd) and that the video card and memory stick are seated correctly. The hard drive, presuming it is IDE should be in the primary channel and the optical drive in the secondary channel. If you do not have a floppy drive you must turn this off in the bios. Most BIOS routines have an optimal setting which includes searching for a floppy drive if there is a port for one on the motherboard. Do not put any installation CD into the optical drive. Your hard drive and optical drive should be recognized. You should hear the first post beep. If there is no operating system on the hard drive and the hardware is working properly you should complete posting and get to the point where you are told there is no operating system. If you do not get to this point you have a hardware problem and could have shorted out your motherboard or some component thereof. If you do not understand even this level of troubleshooting it may be cheaper in the long run to go to a local computer repair place and let them look at what you have . . .