Hi, my computer will not boot up, when I turn it on the fans are on,the motherboard LIGHT is on, the cd/dvd is on, the mouse is on, there is no video signal, no front panel lights and no keyboard, these components work on other sytems and vice versa, also when i hit the power button the computer will not shut off.If you hold in the power button for four or five seconds, will the computer shut off?

Is this a new build, or did you have the computer a while, only to have this just start happening?No ,holding the button for a few seconds does not help, the computer is almost 2 years old.A lot more info on the components involved and how you have ASSEMBLED them along with the OS involved and what happened prior to this and someone will be along shortly...The computer is no name with a Intel Pentium 4 processor, a Seagate barracuda sata hard drive, windows xp os, lg cd/dvd rw, 2 gb memory, 420watt power supply which I did a voltage check on, an Inno video card. the computer may be damaged from a recent move, even with careful packing and handling. I can ACCEPT damage but I am trying to narrow down what rather than swapping out components I DONT have. I have other mice, keyboards, monitors but my other computers are AMD AND THE HARD DRIVES ARE IDE rather than sata. The computer is two years old and I have had no problems. The mother BOARD is Intel Essential Series 775 socket atx form.I would strip it to the minimum then and add one component at a time to see who is the culprit...
CPU
Mouse / keyboard
1 stick of RAM
Vid card
Monitor

My first suspect though is the PSU...see if you can borrow another one of the same or greater wattage and swap it in there to see...Thanks, I will try those swaps and let you know the results soon.You're Welcome...we'll be here.