I have a Dell Dimension 4550 that had a power surge hit it. The case fan would run at wild speeds but nothing else would work. The light on the motherboard would light up. I replaced the power supply and it fried the new supply. I have tried 3 power supply's and same result. I have checked the HD and it's fine.

Any ideas why this is happening?

Thanks!

Mike

when a power surge hits a computer, most of the small, delicate circuits become fried. Your cpu is most likely gone, and maybe your motherboard. Use a surge protector if you can, and make sure to get one with phone line protection as surges can come trough the phone line. My advice would be to get a new cpu, ram, etc. Because the surge came through the psu everything delcate connected to it is most likely gone.

when a surge blows a psu and you replace it with a working one and this one blows aswell then you know the system is damaged, this not good as this could mean a new pc(mainboard,cpu,ram) the best is to replace them all at once, ass you do not know which om them are at fault and might needs some more psu's

Dell do not provide adequate Power supply units. I hope the PSU you replaced the faulty one with was 500 Watts. Anything less is inadequate.