>>Batten down the fan before you blow - sometimes spinning it in the wrong direction with an air jet will farkle the power management buss.
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>I assume you meant "button down" - you almost got booked at The Grand Art of Spell but then I remembered (not immediately, because of your long absence) that you're in a sepErate catAgory, spelling wise.
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>I seem to have such a problem. My dv9000 (running Ubuntu) was getting sort of warm, and since I couldn't find compressed air for a while (*), now that I found it, I decided to give it a quick blowout, without powering down. Which worked - the machine kept on running for a few more days without a hitch. Then I noticed that the external mouse I plugged in isn't recognized, I decided to reboot.
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>Which it refused. It shut down nicely, but won't boot. It spins for a second or two, then just disconnects the fan and all those blue LEDs. If I keep the switch pressed, it will spin the dvd drive for a while, decide that it isn't an audio drive (it can play those out of the BIOS, one of those multimedia laptops), and then just spin down the fan and turn off.
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>No clue how to reset it back to normal.

I think what Terry meant was to stick a pencil or some such in the fan (i.e. "batten down the hatches") to prevent it from turning, before blowing it out with compressed air. If you let it turn, you can grossly overspeed the fan with compressed air and damage its bearings, and at high rotational speed the fan can generate a lot of back EMF/voltage which can damage the mobo if the mobo isn't designed to resist that sort of abuse.

Got a few ideas for you:

1. A client of mine has an HP server, which because of a major power outage decided to go into some sort of standby/hibernate mode, rather than shut down completely as specified by the UPS management software. Pressing the power button, pressing and holding the power button, nothing worked, same symptoms as you describe. The way we finally fixed it was to completely disconnect the server from power for a solid minute, so the motherboard was powered off (on ATX and later systems, the mobo is still powered up whenever the system is connected to power, even if the computer is nominally "off"). After powering off the mobo in this fashion, it started again normally.

Your laptop is a different beast from a server, but still at heart an ATX/ACPI system. There are a few things you can try, alone or in combination:

- Press power button once, briefly (should initiate normal start)
- Press and hold power button for 4 or more seconds (should initiate hard shutdown, but depending on how ACPI and BIOS are configured, might be some other "change state" action)
- Unplug the laptop from mains power, and remove the battery for at least a minute, in order to completely power down its mobo

2. This is kind of a long shot, but maybe the laptop's battery has gone bad. You can test this by removing the battery, plugging the laptop into the mains and seeing if it will start

3. Another long shot - another client with a Dell laptop had a similar reboot problem after a power failure in her home office. The solution in that case was to disconnect the externally-powered Samsung USB printer she was using, which let the laptop boot, then she reconnected the printer to the laptop, and everything was normal. The idea here is to "simplify" - disconnect all external devices except (optionally) mains power, then see if it'll POST and/or boot

4. If still no go, it sounds like some sort of power problem within the laptop itself. Possible causes:

- Component failure (HD, optical drive etc.). A failure can be a partial or dead short in a component, which would cause various bus voltages in the computer to be too low to function. The trick in this case is again, to simplify. Most laptops are modular, it isn't too hard to remove the optical drive, hard drive and any memory chips beyond what is absolutely necessary for the machine to POST and try to boot. In some cases you can even go so far as to remove all the RAM, in which case the machine should give you beep codes while POSTing

- I had one case with a desktop machine, where it had been in use on a shop floor, powered from a 230V outlet. It was then moved into the front office, and plugged into a 120V outlet without anyone sliding the little switch on the rear of the power supply to the 120V setting. This almost certainly doesn't apply in your case, with your laptop, but I thought I'd mention it because the symptoms were *identical* to what you're seeing.

- If you've simplified to the max, and the machine still won't POST, you have a hardware failure - either power supply, or mobo. With desktops a power supply replacement is cheap and easy, but not so much with a laptop.

5. Another general troubleshooting tip - as a rule of thumb, 80% of hardware problems are actually caused by bad contacts. You can unplug any removable components, run some contact cleaner over the connectors and reconnect them. Dust buildup on densely packed surface mount components can cause partial or complete shorts. IOW cleanliness is next to happiness :)

Maybe your compressed-air cleaning effort blew some dust into places it shouldn't be. In that case you might need to do a significant teardown to expose all the electronics and make sure they're clean.