Strange Computer Freezing - Help Please

I have been having strange problems with my 3 year old PC.
It is a Pentium 3 - 500 with 12Gb HDD, and 128 Mb of RAM running Win 98. And I have not added any new hardware or software for over 6 months now.

For many weeks now it has frozen within 0-5 minutes of booting up. I usually leave it in a frozen state then reboot again about 20 minutes later and everything is fine after that and it can stay on for days. I wondered whether this problem was caused by a 'cold' boot, and that the components needed warming up in order to work properly.

But the last week it has not been booting up properly at all. It just freezes within the first few minutes of starting up and even if I reboot a few hours later it still doesnt work. I have booted into BIOS and left it there and it still freezes (so Windows isn't the problem I think). If it does manages to get into safe mode it still freezes soon after.

Power Supply is only a year old and I think its fine. I think the problem is either the motherboard or memory or maybe the hard drive. Any ideas please ?

It's possible that a fan is in the process of dying.

Either the CPU fan, or the fan in the power supply. It can be intermittent.

Basically, if a fan is having a hard time keeping its rated RPM, it's not going to be maintaining the appropriate air flow. They are spec'd to do a job in keeping the power supply and CPU cool.

If you have a 4500 rpm fan running at 1900 rpm, heat is going to become an issue, for the power supply or the CPU (especially the CPU). But how would you know by sight alone that the fan is running 2600 rpm slow?

The fan could, after a few minutes more of running, pick up its RPM.. perhaps the bearings warm up enough to free the friction that was slowing the fan down.

I'd definitely replace the CPU fan as a low cost start. Then either replace the power supply fan (fans are about $4 or $5 here) or the whole power supply ($35 here).

If none of that takes care of it, post back here.

just adding to the heat idea, check for dust build up on all fans and components, even though you have not added anything yourself, this sounds like a auto updater at work, any program could be to blame, anti virus, firewall, works, anything that checks the web in the background, what all do you have in your start up? if you have alot of services starting and you example:anti virus starts updating.........norton, trend(pc cillin), mcafee use alot of resources anyway, on 98 they are a little demanding unless you use a third party software to manage your ram, i dont like to recommend these types of programs,read the description and decide for your self.
http://download.com.com/3000-2086-10070530.html
i would try that one and see if memory leaks/ load-ups are your problem. i have used this program and it works very well

I think I have found the cause of the problem. I replaced the PSU with one I borrowed off someone and it has been fine ever since. I am a bit annoyed as the last one is only 14 months old, but at least I seem to have found the solution. I only discovered this out after I had ordered a new motherboard/processor and memory ! Still it may be time to upgrade anyway.

I also noticed last night that the clock had lost about 9 minutes over the course of 24 hours that the PC was on for. I think I need to replace the CMOS Battery. If I do this will I lose any settings I had made in BIOS ? And how much are CMOS batteries ?

Yes, if you pull the battery, CMOS your settings will be lost. If you have substantial customized settings, jot them down before pulling the battery.

Nine minutes over 24 hrs. is an awfully lot of time drift! You may want to double check to see if the drift is consistent. I didn't think that a low CMOS battery could create a time slow down, as it is not an analog or mechanical clock. I could be wrong, though. Good luck with this.