Hi

The boards in a Viglen Desktop machine, the processor 3.2 intel, 512 ram XP sp3 installed

the problem it will not boot. switch on and the FANS going to top speed but don't come down for it to boot.

I have changed the power pack, from another machine the same thing, but when i put the power pack back in the other machine the same things happened to that ONE.
I did by mistake leave the low voltage connection off the 4 pin black and yellow wires, powered up the fan went high came down the screen showed the intel blue screen, just froze,

Any ideas please.

Also the same things happened to a freind of MINE Dell 520 machine, fan runs high but wont boot.

That is an older motherboard.
Make sure you do the power supply connection right. If you messed up the powr connections, the board MAY be toast.
You can buy a used one in good condition for $50 or even less. But the only reason for buying another would be the CPU and memory. If they are good, get another board. Most likely the CPU and memory would survive, but its not a sure bet.