Any ideas why my computer freezes randomly?

I'm running win2k, never had this problem before. One day one of my hard-drives craps out (I have two in there). Take out the hard-drive and send it in to get another. While waiting, my computer freezes randomly with even one HD in there. It just completely locks up, no beep or anything. Mouse and keyboard stop responding and I have to reboot. I'm wondering if my other HD could have been screwed up too? The only other thing that's really in there is my video card. Pretty much everything else is onboard.

By the way, I reformatted and still no dice. Could this be a driver issue?

Could be one of a million things.

The only time recently that my system would lock up on me so badly like that was because of the Cydoor adware which was very buggy. After running Lavasoft's Ad-Aware and cleaning my system of adware and spyware, my random lockups went away.

I'm not saying that's your problem, I'm just saying the last time that happened to me, it was Cydoor's fault.

As Tony said, it could be a number of different things. The most common that I run into are: faulty/unclean power supply, over heating, faulty memory, and over heating of the memory. Pure lock ups like that are usually caused by one of those four things. Of course, that doesn't mean your problem isn't being caused by something else. Just pointing out the things I've run into the most.

ive recently been havign a spill of bab memory around my home network and a few friends. i would check that out.

A few simple (and free) things you could try:

Run a HDD diagnostic to identify & flag any bad sectors. I've experienced freezing a few times where the Swapfile resides over bad sectors.
Make sure the CPU heatsink gets warm i.e. it's making a good contact with the CPU.
Remove & reseat as much as you can (AGP, DIMMs, IDE cables etc.). Alcohol wipes are good for cleaning the AGP card & DIMM edge connectors.
In BIOS setup, load factory defaults. Additionally, you may also have a pre-defined Safe Setting which may help.

That leaves you about 999,990 other possibilities. Good luck and I hope you track it down

Are you sure the other hard drive went bad? Maybe it's your IDE controller that's going....

I'll run some diagnostics. Also, the freezing normally happens within the first 5 minutes of booting, if that helps. Once I've been running for awhile, it tends to keep going without freezing.

Once I've been running for awhile, it tends to keep going without freezing

That makes a difference how you troubleshoot this, possibly your fault is temperature related. Diagnosing intermittent temperature related problems can be painful and a lot of people instead resort to module swapping which for you could mean costly trial and error.

In simple terms here's my usual approach to this type of fault, I hope it helps you:
Reduce the system to an absolute bare minimum both in terms of hardware and software and be able to reproduce the fault - I think you have done some/all of this already.

Make sure first of all it's not a mechanical problem (possibly a microscopically small bad component connection) by tapping the system board/HDD etc. with a screwdriver handle. See if you can introduce the fault this way and while using common sense where you 'tap' don't be shy Wiggle cables too plus anything else that's connected.

Moving on....
Use a hair dryer with a home made 'funnel' to give a narrow (more specific) hot air stream or some other heat source and with the aid of a piece of card (as a heat shield) warm isolated parts of the system and note the effect. Similiarly, using a can of freezer spray (available from electronics shops) chill parts of the system and note the effect.

Hopefully you will see a failure pattern emerge and begin to narrow down where the problem lies. What is vital is that you demonstrate to yourself a good degree of repeatability of fault present / fault not present before you can be certain of your findings.

Ok, I think I've narrowed it down a bit. I'm pretty sure it must be one of the main hardware components because it has even locked up while in BIOS, just changing around settings. It's not the RAM, I've replaced the chip and tried different slots. I don't think it's cooling, heat sink is warm, all fans are spinning, but nothing seems overly hot. It's neither hard-drive, because I've hooked them up independently and on both IDE channels. The only other thing I can think of, as mentioned, is power supply. How could I go about making sure that's it? Is there anyway to without buying another one just to see? Do you think it could be something loose inside and would be an easy fix, or are they pretty complicated devices?

Thanks

In your situation it's rare (but certainly not impossible) for PSUs to exhibit this fault behaviour.

IMO you need to provide more feedback regarding your troubleshooting vs. the suggestions already given to you in this thread to get anything better than a mere guess at either: CPU, motherboard, VGA etc. etc.

Well, I think I fixed it, but still don't know for sure what it was. I thought it was the video card for awhile, but I tried another AGP card and a PCI card when it kept freezing to make sure. I then tried the suggested blow drier on specific parts of the computer to check for overheating, and that didn't cause any freezing either. When I used the box as a drum set, it seem to freeze when I got up to a specific bpm , so I assumed something was loose. I reconnected pretty much every cable in there, and no freezes for a day. Thanks for the help guys.