Well, take it by the numbers.
First you should see the comments on the screen, but there by the bios, and after that you should see the first signs that Windows is loading.
In that first second or two, you should also hear your system speaker let out a single "BEEP". The beep is a sign that the boot program in the motherboard has finished its job. No BEEP, No Boot!
So are you hearing the beep? Probably NOT!
The first thing I'd check is the CMOS battery on the motherboard.
If the mobo is over four year old, I'd just replace the battery with a new one.
Remove all power from the computer (unplug the power cord) then remove the cmos battery on the motherboard. Make sure you leave it out for at least 15 to 20 minutes. Then replace it with a new battery, replace the power cord and try to boot up the system again.
In many cases, this has worked for me to revive a seemingly DEAD system.
Good Luck,
The Doctor
