Hello Yi:
Unfortunately, your laptop may be toast. Here are a few cheap and easy
things you can try:
1) Try a different AC adapter.
2) Try it with the battery removed.
3) Try installing a new battery.
4) Try removing and reseating any removable components: disks drives,
memory, min-PCI cards.
If none of those fails to make any change, most likely your motherboard
has gone south. Replacing the motherboard in a laptop will likely cost big
bucks. It is up to you to decide whether reviving your laptop is worth the
cost.

regards,
bruce

"Yi Qiang" wrote in message
om...
hi,
My presario 1720US stopped booting yesterday, the power won't even
turn on. When I plug in my ac adaptor, the black bar's light is
supposed to be solid green, but not it just flashes. The battery
won't charge, and the laptop won't boot at all. Can anyone tell me
what the flashing means? (The black bar that is the AC Adaptor has a
little LED, and if I remember correctly under normal conditions it's
supposed to be solid green.)

Thanks