PC Won't power on

[toddyo1388]

PC's been running fine, now all of a sudden it won't power on using the front panel switch.  When the switch on the power supply is turned on, all the case fans and the proc fans spin for a second and the green light on the motherboard indicating power comes on and stays on steady.  I thought at first that the power switch might have gone bad, so I bypassed it by using a jumper to short the power switch leads on the motherboard, but still no go.  Here are the specs:

ASUS A7N266-VM motherboard (onboard video/sound)
512MB Corsair ValueSelect PC2100 RAM
Athlon XP2000 proc
300W power supply
Western Digital 80GB HD

Nothing else connected right now, for testing purposes.  This is my wife's aunt's PC that I built for her.  I've only been able to tshoot what I could while I've been at her house, but I plan on taking the PC to my house this weekend for further dismantling.  My next step was going to be removing the mobo from the case to make sure there's not a short.  Any other ideas??

[Kablam]

Made any adjustments to your setup recently or just before you had the problems

[toddyo1388]

Made any adjustments to your setup recently or just before you had the problems

None that I know of...  As I said, this isn't my PC, but one I built for a family member.  She never uses the PC unless it's me doing something for her or my sister-in-law over there playing games.  Hardware-wise nothing has changed since the PC was built almost a year and a half ago.