Nothing is recognised, whats going on?

OK. I just built a computer and it has a problem, it doesn't recognise the keyboard, mouse, and monitor on startup. The system does not beep, and I've checked the RAM, processor, etc for functionality. What would be the problem. Oh and specs:

Intel Core 2 Duo E6600 Processor
Intel 945GCLL Socket 775 MicroATX Motherboard
Kingston 1024 MB PC5400 DDR2 RAM
Lite-On DVD+/- R/RW Dual Layer, DVD-RAM, Lightscribe, etc
Seagate 160GB 7200RPM 8MB SATA Hard Drive
Antec Case w/ 400 watt PSU

Dell Keyboard, Mouse, 17" LCD monitor

 

So no image/no video at all? or just delay?
If your getting no Video images at all, first suspects are Power problems connections or inadequate psu, or even a Short or grounding condition
Other thing's that cause no video are bad VC or Memory or improperly seated VC or Memory

Is your Keyboard/Mouse USB? best to use PS2 for setup of new build

Your 400w PSU what exact brand?

Your system does not beep, do you have an onboard speaker connected? some may be onboard mobo some are or come with the case (not external speakers)
I have a jumper on one of my MOBO's to enable the onboard diagnostic speaker
Are you sure the onboard speaker is connected or connected properly (grounded MOBO's will usually not have any diagnostic beeps)