i recently purchased a used dell optiplex gx400 1.7 ghz p4 512 mb rdram. it worked fine for about 3 months untill acouple days ago when it basically stopped working. when i turn it on, it powers up and does nothing. the power LED is solid green and indicates that everything is okay, but the monitor doesnt display anything and the computer wont POST or boot or anything. i suspect possible RAM failure but i am not positive. i went on www.dell.com and searched their support options, it mentioned the LED diagnostic lights on the back and said it was "possible memory subsystem error or failure" and suggested "resetting the BIOS" using the jumpers, which i am not sure how to do as the "online users guide" provided by dell was not much help. can anyone help?

See if you can find the motherboard manual from the support site. If not, then you'll have to look at the mobo itself to see if you can locate the jumpers. They're usually along the left edge of the board (CPU in upper right). You'll have to look at the silk-screen printing to see which ones to use and how to set them.

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on the support website it says, " STEP: Reset the BIOS using the RTCRST jumper, CLR CM jumper or CONFIG jumper. [Desktops]." then it suggests consulting the "online users guide" for information, which doesn't say anything about resetting BIOS and the only jumpers on the MOBO are the RTCRST jumper and a PASSWORD jumper. the password jumper has a cap on it, the RTCRST one doesnt. i didnt even know that these "jumpers" existed untill now so i have no idea how to use them i read on a different site that someone had a similar problem but only one reply was posted, which didnt help.

Does your computer make a series of beeps when you turn the PC on?
You might want to check all your hardware and make sure it's all plugged in properly.
If you here a series of fast beeps when booting the pc the issue is related to your Video Card. Maybe the video card was loosened from the AGP/PCI slot or something like that?

If you have a spare jumper (there's often one on a hard drive or on a motherboard jumper that isn't closed), connect it to the RTCRST jumper to close it. That should reset the BIOS when you next boot. Make sure to remove the jumper when you're done, otherwise it will keep resetting it.

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first off, thank you for your replies. secondly, i found a spare jumper and closed the RTCRST jumper, but when i attempt to power on nothing happens at all when i push the button. if i then remove the jumper, it powers on but doesnt POST or beep or anything other then spin the fans and display the same, " memory subsystem activity or failure" sequence on the diagnostic lights.
the HD makes acouple sounds too and the HD activity light on the front lights up. the lights on the keyboard flash when i try to boot but then the keyboard becomes unresponsive. the Num Lock light doesnt come on, nor does the Scroll Lock light.

To me this sounds more like a motherboard issue... If you really want to get this taken care of you might want to test this theory by replacing your memory one stick at a time to see if that makes a differenece. If that doesn't work replace the CPU as well. Make sure you unplug everything except your video card before doing any of this. If you don't have any spare parts try to find a friend that has a pc with a CPU and RAM that will fit on your motherboard.

Other things to look for in regards to your motherboard are the capacitors.
The attached picture shows some capacitors that are good (sorry about the quality) Good capacitors are flat at the top like the ones shown. If they go bad most of the time they become rounded, kind of bubbling out at the top. If you see anything like this I can Guarantee it's your motherboard.

Attached Images

capacitor.jpg (40.1 KB, 84 views)

well, i searched all around the MOBO and checked all the capacitors i could find, they all seemed to be normal and flat on top. as for the memory. my system uses PC800 RDRAM RIMMs, which are somewhat pricey and can be hard to find. is there anyway to determine if the RAM is fried be looking at the casing or something. i'm pretty sure that no one i know has a computer that uses similar RAM so i cant try it in a different computer, or even borrow some to try in mine. since the RAM is so expensive i would rather avoid purchasing any unless i learn that it needs replacing. i'm at a loss for spare hardware and components. i will have to check with one of my buddies at work to see what sorts of stuff he has lying around

You might want to call around to local PC repair shops to see if they have a RAM tester. But I have to say....I don't think I would go that route, this really seems to be more of a motherboard issue than a RAM issue.

Another thing you can do is turn the PC on with everything removed (RAM and CPU included) except for the Video card. This is all designed to tell the PC you have a CPU/RAM issue. I'm curious if your motherboard gives any of the diagnostic beeps that it should give if something is wrong. With all of the above being removed you should be getting a slow and consistent beep. (Beeeep Beeeep Beeeep) This beep is indicative of a RAM/CPU issue. If you don't get the Beeeeps like you should I would defenitely lean towards it being a motherboard issue than anything else. Try that and get back to me with what you hear.

It's been a while since I've done this sort of thing so if anyone has any input that I might have missed that would be great!

i removed the RAM and it beeps like crazy when i turn it on. all long beeps.
first 5 long beeps, then 2, then 2, then 1