Which component is broken?

[moola]

Hi.
I am going to have you guys help me build a new PC but I want to fix the old one first.
My specs are 2.66mhz pentium 4 and 512mb memory and 30g of storage.
when i plug it in and press the on button nothing happens at all. it is a emachines pc on windows xp.
What is the problem?

[c_hegge]

Fleamachines from that era had those Bestec (Worstec) ATX-250-12E PSUs with the killer 5vsb, so my guess is that the motherboard has been Bestec'd.

[moola]

i am sorry what is a 5vsb? should i replace that?

[c_hegge]

the 5vsb is a circuit inside the Power supply, short for 5 volt Standby. It provides 5 volts of power to the motherboard when the system is off. The Bestec ATX-250-12E has a known problem where the voltage on that rail goes too high after a few years and fries the motherboard. You will need to replace both the motherboard AND Power supply.

[bharath]

can you tell more about SMPS also did you seen backside of your PC where cooling fan is working or not.Look on this site and see if your product listed http://www.emachines.com/
let me know if their any help needed i can surely help to you whatever i can

[moola]

Oh yes my power unit is a Bestec atx 250w 12e. The fan on the power unit does not spin either and it looks rather dusty. I will order a replacement. Could somebody please advise one?

[shovenose]

I would recommend this one:
http://www.newegg.com/Product/Product.a ... 6817104951
It's cheap and a relatively reliable brand. The capacitors used in it aren't that great, but they are on par with the ones in your Bestec, it won't fry your motherboard, and it has more output power so you can add more upgrades to your computer further down the road.
Unfortuntely there is no way to tell if your motherboard is fried by the Bestec. You're just going to have to get the new one and see.

[c_hegge]

Those PSUs amlost always cook the motherboards when they die.