Try draining the static electricity from the board. If that doesn't work then most likely it a cable or board issue. Also does the power light turn on or do you hear a system sound, or is it completely dead?
I saw a good wright up of directions on how to do this on another forum, also at the end see a link to the manual which shoes how to open up the cover and remove the battery. While you have the machine open double check that the cable from the power button isn't loose.
"...you should be starting by resetting your BIOS, and you can do this by removing the outer casing o the PC tower. Once yoiu have done this you then need to find the jumper that clears the CMOS/ BIOS. Now if you are somewhat unsure of what a jumper switch is, it just consists of a smallplatic cap which covers two metal conductive pins on the motherboard. There is usually a pin which is not covered.
Now once you have found the CMOS/ BIOS jumper setting, you will need to first remove the motherboard battery. The battery is nothing more than a glorified watch battery of the CR2032 type, and it will be silver in colour and obviously round in shape (typical cell battery).
Once you have removed the battery, you will need to then clear the CMOS/ BIOS and this is done by moving that jumper switch into the clear position. The pin that is exposed will need to be covered withthe plastic jumper, and the pin on the opposite side will need to be exposed. Leave the jumper in the clear position for about 10-20 seconds or so, and then replace it back to the original position. (doing this discharges all of the electricity in the BIOS/ CMOS chip). Once you have done this, you put the battery back in place and then start the machine, then you are good to go...."