Last week, my computer started having problems suddenly, after running fine for months. There began a click-click sound, like a light switch being turned on and off. The computer began rebooting randomly. I began to get blue screens with stop error messages (mostly 7A messages, but also others). Shortcuts disappeared from the desk top. CD/RW drive would sometimes work, sometimes not. The system would lock up. The event logs are filled with errors and warnings. I am getting all sorts of weird pop ups, which I didn't have before. I thought it was a virus, because I had recently downloaded some screen savers, however every virus program I've run says there is no infection. I have not changed anything nor have I added any new programs (with the exception of several screensavers I downloaded...I've removed them. I thought the the Master Boot Record was corrupted. I replaced the HD with one I knew was fine, but the same thing happened. I've even wiped the disk, reformated it and written zeros to it and reinstalled the O/S: no luck. I've tried everything I can think of and am at the end of my rope. It seems like it has a hard time booting up to the O/S when cold, and seems to run smoother when warmed up, however, it still has the same problems even when warm: ie: unexpected reboots, errors, etc. Someone please help me...tell me what might be causing this and how to fix it. I have an IBM clone using a AMD Duron Processor with 97,776 KB of RAM, running windows 2000. Thanks for any help you can give me!

Welcome to the PC Guide Forums

This is a hardware problem. One of your devices is fritzing out - probably shorting.

You will need to try to isolate the cause. I would first try disconnecting all of your drives except the boot hard drive. Remove all cards except for the video card. Then boot and see if it still crashes. If so, you have narrowed the search for the bad component.

And don't forget to leave in one stick of RAM to start with in addition to what Gwallen said.

The click-click sound makes me think hard drive, so get the drive manufacturer's diagnostics software from their website and run it.

Spontaneous reboots are most often related to heat or failing power supply. Take the case cover off and clean out the dust inside, run it with a small desk fan blowing inside to test for heat related problems.

The stop messages, icons acting up etc could point to bad memory, corrupted files, virus or spyware, hard drive failure could also be related.

Weird pop ups...a better description of that would be a good idea. Weird popups after downloading screensavers smells like spyware to me. But let's eliminate hardware before we go any further...Hard drive diagnostics, bare-bones boot might be in order, and a good memory tester might be worth trying too. Memtest (http://hcidesign.com/memtest/download.html) has a good reputation.

Thank you for the suggestions. I tried removing everything and booting up. Still the same problem. Swapped out HD, still the same. The clicking noise is definitely coming from the HD, even after swapping out with one I know is good. I'm wondering if maybe the power supply could be going bad. I noticed the CD drives speeding up and slowing down, and then running wildly. Could that be whats causing all this havoc?

Okay. So you have isolated the problem to motherboard, CPU (unlikely), memory, video card, or power supply.

You could try your memory one stick at a time, or use the software memory tester mentioned above. It would be nice if you couold get a different power supply and video card to try.

Take a good look at the capacitors on your motherboard (look like little silos) to see if their tops are bulging.

Thanks for the fast reply! The capacitors look OK. I ran Memtest and it came up fine also. The video card looks strange. Rather than a card, it looks like a block of colored plastic---never seen that before. I'll try to get another power supply to try in it. Do you know of any test programs that can test those components? I checked the device properties for all my hardware listed in the windows control panel system program, and it lists that everything is working properly. Can that be deceiving? I don't know much about that.
Thanks again for all your help. I am really a neophyte when it comes to computer hardware.

Malfunctioning devices can show up in the Device Manager as being perfectly fine.

Really the only way to test video cards or any device is to try them in a computer and see if they work.

Download a copy of my diagnostic flowcharts from here
www.erniek.eclipse.co.uk/downloads/sylvanderdiags.zip
and print them.

Begin on the START UP chart.
You will probably be taken to the NO POST chart.
Assuming that the PSU is fault free [it may not be] and all peripherals and adaptor cards except the keyboard and monitor have been removed and POST still does not complete then "the system board or something on it is faulty".

Consider the BIOS and its configuration settings [in the BIOS Setup] to be part of the motherboard.

You should consider noting all the present settings and "load setup defaults".
See if you notice any settings that are obviously wrong.

A link to this power supply tester http://tinyurl.com/lrkr is included in note 1 on the SYSTEM chart.