Wikipedia is a great source for information about motherboards, RAM timings, processor cores, and so on. For example, from http://en.wikipedia.org/wiki/Socket_A I learned that Socket A is the same as Socket 462.
Hopefully that'll help you some.
Yes, great. Thanks
http://www.ebuyer.com/UK/product/102909
You need to consider the possibility of upgrading this computer as an alternative to simply replacing the motherboard. All modern motherboards will require the same set of components: A PCI-Express video card, DDR2 RAM, and a 24-pin ATX2.0 PSU. You have none of these at present, so moving to the latest CPU will not be possible without purchasing what is in essence an entirely new CPU. Unfortunately, most of these components are mutually incompatible with what you do have, with the exception of the PSU.
So the difficulty is in breaking the upgrade into as many smaller, discreet steps as possible, each resulting in a fully working PC with greater performance than previously. Ideally, the steps should avoid repeated replacement of individual pieces of hardware too many times (buying 4 or 5 different motherboards to upgrade the computer would be aggravating).
As I see it, you have 4 choices. All but the first would require a new PSU, but since your's is broken and 24-pin ATX2.0 PSUs are around the same price as ones which wouldn't support a new motherboard, it doesn't really require consideration - get a new 24-pin PSU regardless. Anyway:
1) Simply replace the motherboard with another Socket A motherboard. This will cost approximately US$50, unless you must replace the CPU as well, in which case it will be approximately US$100.
This option involves no upgrading of course, and results in a computer equally difficult to upgrade. It also results in spending money on components which will have to be thrown out during ANY future upgrading.
If go with this option and you have to buy a new CPU, you will be paying pretty much the same price as the first step of either of the other upgrade paths, but have a slower, less upgradeable computer at the end.
2) Replace the motherboard with a Socket 754 motherboard, and the CPU with a Sempron64. This will cost approximately US$100.
This will get you a faster CPU, however you will have to first purchase a motherboard with AGP support and then purchase a new motherboard with PCI-Express support when upgrading the video card. But no new CPUs are being made available for this motherboard, so if you choose to stick with it for a while, a non-dual core CPU is the best you can get. It will also provide no means of upgrading to DDR2 memory. Still, it is possible:
A) New AGP motherboard + CPU ($100)
B) New PCI-E motherboard + PCI-Express video card ($50 + ~$150)
C) New DDR2 memory, new motherboard, new CPU (~$200 + $50-$150 + ~$150)
For the final step, you'd choose whatever the current CPU/socket type is and simply pay the price of the DDR2 memory at the same time.
3) Replace the motherboard and CPU with Socket LGA 775 (Also called Socket T, apparently). This would get you a Celeron D, also with 64-bit support, and allow you to continue upgrading the CPU through a Core 2 Duo, although the cheaper motherboards (which include every motherboard with AGP slots) don't support the Core2. Again you run into the problem of having to get a motherboard with EITHER AGP or PCI-E, but this time there ARE motherboards which support DDR2 RAM. So your upgrade path would be:
A) New AGP motherboard with DDR/DDR2 support + Celeron D ($100)
B) New DDR2 memory (~$200)
C) New PCI-E motherboard + PCI-E video card ($50-$150 + ~$150)
D) New CPU (~$150)
Of course, the last step is optional, and would be an ongoing process until LGA775 is dead. Plus you'd wait until whatever CPU is at whatever price level you're comfortable with.
So both of the latter options would cost almost the same amount, but going the Intel route would let you space out the purchases into smaller groupings, and also save you the purchase of a final motherboard (until the one you selected in 3.C. no longer supported the latest CPUs, but that's going to happen with anything).
Also, ECS makes motherboards for both Socket 754 and LGA775 that support BOTH PCI-E and AGP, but the AGP port is a hack tying several PCI ports together, and is apparently slower than a real AGP port and requires one of a small handful of supported cards. Still, if you have one of the supported cards, it might be worth exploring getting this board. The LGA775 one supports both DDR and DDR2, and costs about $60.
And a final possibility is getting a Socket 754 motherboard with a PCI-E slot and embedded video, throwing away the AGP card, and upgrading the video card later. You won't be able to play games until you get a "real" video card, but the embedded video will work for desktop use. And the motherboard can be used as the base of a Home Theatre PC after upgrading to a socket type with support for the latest CPUs.
Sorry if I went on and on, but this is the same thing facing me at the moment, with the exception that I went with Option 1 4 months ago and am now realizing that I now need to throw out my new Socket A motherboard as part of any upgrade plans. I'm leaning toward going with LGA775, and even though I could get the ECS motherboard, I'd have to throw it out when I wanted to move up to a dual-core CPU anyway, so I'm thinking I might as well get something that I KNOW will work with my AGP card and throw it away when I move up to PCI-E, getting a good motherboard at that time.
I'm also sorry I can't provide any sort of UK store suggestions or links, and sorry about giving US prices, but I assume that even if the prices aren't exactly equivalent, the ratios will be.
If I were you, I would buy an AGP LGA775 motherboard with support for both DDR and DDR2 memory and a new Celeron D CPU. That would be more expensive than just getting a new Socket A motherboard, but if it turns out your CPU is also dead it will end up being the same price and much better too. Actually, I guess if I were you I would find someone with a working Socket A computer and convince them to let me drop their CPU into their motherboard for a quick test 
Buying a cheap no-name motherboard to replace my beautiful ABIT NF7S-v2 worked out for me, BTW, aside from it being money shoved into a dead-end socket type.
P.S. You haven't said if you tried out Jan's suggestion in the comments of your last post to try powering up the PSU while it is disconnected from everything but the wall socket (by jamming a wire between two specific pins in the ATX connector). Without doing that, you can't be certain that the PSU really is dead, since a dead motherboard would prevent it from powering up, and I've seen cases where dead HDs, etc. have stopped the PSU from powering up too.
You also didn't say if you saw any bulged capacitors on the motherboard, which would be a sure sign it is the motherboard, and mean your CPU is probably still OK. The only time I've ever heard a capacitor go it made a loud metallic bang that made everyone around instinctively half-duck, but I imagine a slower cooking of the capacitor could make crackling noises over several days. More likely it would be the sound of a PSU dying and then frying a motherboard and who knows what else, I suppose.
Thank you anonymous.
I did check the motherboard for bulging capacitors - none in sight.
I *didn't* check the PSU by wiring pins together. Instead I tested it on another old (circa 199
motherboard I have.
The dead PSU *doesn't* power up on this, a 230W one I have does power up.
Neither of these two PSUs power up when connected to the motherboard.
I'm actually going to give this computer to a friend. It will replace his Pentium II machine, and should be powerful enough for him for several years. (By which time anything I buy new now will also be obsolete).
I'm going down the cheapskate route and hoping that I only have to replace the motherboard.
Commenting by HaloScan
