Question : Problem: computer: Immediate shut down after one beep, no boot screen

My computer just decided to die on me today. Well, this has happened before, but all I did before was unplug the power supply and wait a few minutes, and it fixes itself somehow..

not today. Here's the youtube video:
http://www.youtube.com/watch?v=slgG7r_o-3Q
(sorry about that expletive)

It's not that visible in the video, but there's a decent amount of dust in there.. is it the dust causing it?

The spec is as follows:
cpu: Core 2 Quad Q6600
motherboard: GIGABYTE EP45 - DS3P
ram: Kingston KVR8002N5 - 1G
HDD: Seagate 320GB SATA II
VGA: ASUS EN9800GTHB - HTDI - 1G
DVD/w : PIONEER 216BK
Sound Card: on board
case: ATX-MIDI

The power supply seems to be "GW 550sel", I think GW stands for Great Wall.

So yeah, any definite ideas? I'm about to try swap the video card from another computer to this one, but yeah..

Also, I unplugged the whole thing, and started vacuuming the dust away, from the fans using a makeshift paper pipe (to get to the small places). It's relatively cleaner now.

I plugged it in, it made it through the boot screen, and booted my ubuntu. A while later though, the screen etc just froze with no response. After a forced shutdown, booting again leads to the same situation as shown in the video..

so could this be a PSU problem?

Answer : Problem: computer: Immediate shut down after one beep, no boot screen

Here my troubleshooting procedure :
clean the system from dust, then  test with the minimum setup - disconnect also all peripherals and network cables :
connect only  motherboard + cpu + 1 ram stick, video card, power supply
verify that the 4-pin cpu Aux power plug is connected
on boot, do you have a display?
if NO it is one of the connected, swap ram, Power supply, video card or monitor - leaving only motherboard and cpu
if Yes, add devices till the problem shows

you can also check the motherboard for bad capacitors as shown here :   www.badcaps.net

additional tests and things to try :
boot without ram, it should beep; (also, without video card)
try bios default settings,(if possible) or clear the bios by removing AC and bios battery

answers : yes it can be caused by dust, and yes it can be the PSU - only way to test is clean the system, and test with another PSU, or test this one on another system