PC does not turn on.

[Eternity[LK]]

Hi.

My PC has been running well for 3.5 years. Worst issues I have had were some viruses but I handled them easily, and last virus infection was 5-6 months ago.
I'm not a tech guy, and I have not messed with my PC's hardware. I have cleaned the dust out regularly, with anti-static brush. What I'm afraid most of is the motherboard being dead.

Technical information, what I can remember:
OS: Windows XP SP2.
Processor: Intel Duo Core 2.7 ghz
RAM: 2*512 mb
Power supply: Codegen 350x, 350 W
HDD: SATA II 160 GB
Video: ATI Radeon 128 MB
Motherboard: not sure, no labels on it anywhere...
Lite-on DVD-RW drive

Problem:
When I turned the PC on, the monitor would not turn on, and DVD drive kept turning off/on. I mean, the green LED on dvd drive turned on. Then it turned off. Then the sound indicating that DVD drive has turned on happened again. And it kept doing this for couple minutes. I disconnected DVD drive, and it did not fix anything.
Fans are working, and red HDD LED on PC is blinking.

Tell me if you need more information or have suggestions on what to check.

Thanks.

[caperjack]

process of elimination might help ,remove ram one stick at a time ,if you have on-board video try removing the 128video card and using on-board connection ,ect ect ect

[altuin]

Try another power supply if you have one available. If the HDD led blinks like when Windows is loading and the display has no signal then your video card is busted or the connection from the display to the video card is loose.