Rant and advice request on 2 pcs dying in a week

NOTE: this is a long story but hang in there, I tried to make it a little entertaining too. And I could use some advice on the puzzling thing that happened to PC#4 as I thought I had seen it all and that one is new to me.

I am telling it as a story because I am stumped and I dont know what is relevant anymore.

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The story starts quite innocently...

We're a 2 person household here, spread between 2 houses which are quite far away. Which means that shuffling PCs and screens around got old real quick.

So the solution was to buy enough bits to do a new computer, so we would have 4, 2 in each location.

While I was at it I bought new cases for all of them, cause the old cases all had started having broken doors or usb ports and all. Besides the Antec Solo is a great case with nice soundproofing at a great price and once one of the PCs had it all the others had to have it too.

Sounds harmless so far, right? PC1 and 2 are alive and singing.

-- sounds of birds singing and all --

Of course it got worse when we did the others, which were for the most part just moving the old stuff to a new case

-- ominous music --

(updated)

PC3 was my old main PC, now my secondary machine back at home.
I changed *nothing* on that PC, all we did was move components to the new case.

PC3, the specs

- antec true power 380W PSU
- abit nf7 v2.0
- athlon xp 3200
- 1.5 gb of nondescript ddr ram
- sapphire 9800 Pro (the silent version, cant remember what they call it)
- big massive hedgehog style heatsink with silenx fan
- 2 120Gb Seagate IDE drive, the most silent model they made in IDE
- the usual set of silent fans, quiet DVD drive, rubber grommets, vibration dampeners

The story

All of these had been stable for ever in my old case

So anyway we move all of this to the new case, plug it all in, turn power on. PSU blows

We grab another PSU off ebay, wait 2 days, plug new PSU in.

PSU doesnt blow (that's progress) but nothing appears on screen.

Weird smell - wire on the case-sound-connectors is smoking

Panic, pull power cable off

Unplug sound connector cable, try again.

Nothing fries, but nothing starts either. No HD activity beyond power up. I think Mobo wont post

In Summary (updated)

Some of mobo / ram / cpu must be considered dead
Will power up, all fans except northbridge fan power up, light on mobo light up
I think it doesn't post - I dont even have a pc speaker to be sure, trying to get my hands on one
ram seems fine in other pc

Small Interlude, my other PC goes on strike

PC4 - In Summary

Was moved to new case recently but has been working
Stopped working when changing some external connections - VGA and sound!!!
AGP card confirmed working in another pc. Cant do the same for DDR or CPU at the moment unless I try on dead pc3
I think it won't post - I dont even have a pc speaker to be sure, trying to get my hands on one

FIX
Remove and put back all components
Reset CMOS

It works again

I Still dont understand how this could have upset the machine! And I really didnt need that when the other PC is already playing dead!!