I had bought a Asus pc less than a year.I take it to format at computer shop last month and the workers used their own cd to install all the hardwares,I think it is not the cause of the problem.
Since 3weeks ago,when I switch on computer for too long(bout 7hrs),sometimes it will hang when I playing full screen 3Dgame and if the computer doesn't hang,when I try to turn off and turn on the switch back and start the pc,continuous beep sound will occur for 3-4sec and my monitor is in standby mode but the cpu still running as usual.I click everything but my monitor still no response but I can still turn off the cpu by pressing alt+f4 without looking at the screen.After 2hours and the cpu is cooling down,my computer funtions as normal.This is kinda weird because I didn't face this problem before this.Now I am trying to use my pc less than 4hours and the problem still occur RANDOMLY and sometimes it is normal.If I use computer for 7hours+ the problem(countinuous beep sounds) will SURELY occur when I reboot my pc.

here is my graphic card's information:
GeForce 8600 GT
256MB
screen resolution: 1400x900

I don't know is neither my VGA driver problem nor my power supply problem.Hope I can get some help from here.
Thank you very much for replying and reading my thread.

What I need is information on your computer. First off what is the make/model of your computer or motherboard? Second what is the BIOS? If you can get it to boot with video I need you to hit the pause/break button just after the memory test where it shows you how much ram it has. You will need to be quick and stop it at just the right time. Also is the card under warranty? If it is I suggest contacting the manufacturer for a return.

You should also take out your card to check for burst, bulging or leaking capacitors. Check your card against the screen shots and you might either want to print the article out in color or have it available on another computer while you check it out. If you find any on your card it will have to be replaced.

Warning: to prevent damage to your computer and its parts touch your hand on a metal surface on the case, such as the door frame, before touching anything. Preferably don't stand on carpet. Also only touch the side of the card or the metal bracket on the card. Do not touch any object on the card or especially the gold connectors even if you want to.

Also if you get the beeps again, that is a beep code from your computer to help you figure out what is wrong and is quite useful especially if you have no video. You should notice that there is a pattern to the beeps. I need to know what that pattern is in terms in number of long and/or short beeps. The BIOS manufacturer will have information on what that sequence means.

Thanks for reply.
Here is the information:
Motherboard: ASUS P5K SE/EPU
Warranty : 3years limited warranty
BIOS version : American Megatrends Inc.0304
SMBIOS version : 2.4

I can still taking screen shots and printing out from my pc.
The number of beep sound is 4beep.Frequency is like | ||| (beep~beepbeepbeep), the first beep is a lil longer than the other 3 which are short one.It just beep one time when I switch on the computer and is not repeating.
And if the computer goes normal,the beep sound is only once and is a short one.

Thanks again for helping me.

Sorry I'm so late getting back to you but yes in most computers (by convention) one beep under a normal boot up is all you hear so you want one beep. More beeps, no beeps, or an un-ending beep is bad. I'll research and get back to you.

This isn't enough info. Please see here for information on how to determine what BIOS version that you have.

Hi townsbg.I have searched at internet and the beeps sounds defined as : no VGA detected. Problem getting worse now,I can't even start my computer for whole yesterday. What I want to ask is would virus in my computer preventing my computer to detect VGA? I can't follow your way to determine my BIOS version,now I'm even difficult to boot my computer. What else I can do now?

Thanks again for helping me.

Try clearing your CMOS. From your manual:

Have you taken out the card to examine it like I previously suggested?

You should also take out your card to check for burst, bulging or leaking capacitors. Check your card against the screen shots and you might either want to print the article out in color or have it available on another computer while you check it out. If you find any on your card it will have to be replaced.

Warning: to prevent damage to your computer and its parts touch your hand on a metal surface on the case, such as the door frame, before touching anything. Preferably don't stand on carpet. Also only touch the side of the card or the metal bracket on the card. Do not touch any object on the card or especially the gold connectors even if you want to.

I checked my graphic card and it doesn't have the problem.
I found that my computer can become normal when I unplug all the connection wire at cpu and re-plug it again,and it can last for 2-3days and no beep sounds occur,after 2-3days it occur again.damn.
I will try jephree's way and give the result soon.
And if my pc hang when I playing 3D game,what make it become like that?

Thanks again for townsbg and jephree for helping me.

Is it a 4-prong wire that looks about like a square? How many different wires? Are they bundles of wires or cables?