Hi, I just got a old PIII out of the bin (company's room clearance, it's christmas !). I turned it on, it booted NT4, fine, I went for a coffee. When back, there was no signal on the screen anymore and it was dead. When open, I saw that all 7 capacitors are like... pregnant, with powder around. From anyone's experience, is this just the top of the iceberg or would the mobo be likely to run fine once the caps are replaced ? I mean I can get a cheap mobo on ebay if it's not worth the effort, but if the chance is 1/2, i'd give it a try. Anyone done it with success ?

Sometimes duff caps can damage components further down the circuit (particularly other caps). Sometimes replacing the caps makes everything hunky dory.

To replace caps you need equal or better caps (>=voltage, same uf rating), a 60-watt soldering iron, a solder sucker, maybe some desoldering braid, a toothbrush, isopropyl alcohol, and ideally 2% silver 60/40 solder.

Often-recommended quality caps are Samxon and (what I use) Rubycon. They should be labeled as Ultra- or just Low-ESR caps. As for soldering irons, lots of people recommend Weller irons, but any 60W soldering station will do. A 2 to 3mm tip and a very pointy tip are all you need. A little pot of tinning & cleaning "grey stuff" is useful sometimes, too.

I have done it with less, 25W normal iron with thin tip and you don’t even need to use 2% silver 60/40 solder, just electronics solder with resin will do the trick. It could be that I’m more experienced in this kind of work, but I can replace a cap with solder and iron (yes ONLY those) in 30 seconds.

I'd love to see you cut off the excess metal with your teeth

For info, I did and it works. I've been running mem, mobo and CPU tests for 2 hours without problem.
I replaced all big and medium caps (19 in total) with a bit of patience and about 8 euro. Not really cost effective but hey... it works !

Yup, it’s really easy to do. 19 Capacitors, wow, you knocked your self out there! Where they all that bad? Normally you only replace the ones around the voltage regulators...

By the way, if you bend the metal wire to much it will break by it self .

More than half of the big ones looked bad. I went the safe way. For the record, the mobo is fine now but the PSU is not reliable and is it's not a standard factor (or one I that's not common), so I got a working mobo with a 1Gig Celeron. Great .