New pc did work now doesn't, please help

[rjob]

i have just finished building a new pc, turned it on for the first time yesterday and it was working fine. came today to turn it on and nothing, i've taken out all the connectors and rechecked them but nothing, all that happens is the led on the motherboard turns on and the psu makes some sort of noise (not the fan) but it doesn't power up at all which i find surpising as it was fine for the few hours i had it on yesterday. oh and this is the first pc i have built from scratch

the specs.

asus k8n motherboard
amd64 3400+
1gb ddr
2 sata 160gb hdd
peak radeon 9550 graphics card
sony dvd+/-rw
400w psu

think thats it, please help

 

[Liquidlen]

Welcome to Techspot!

If you are saying there is no fan starting PSU,CPU or case ,no power.
You gotta start by returning that PSU and try another.

 

[fishhookz]

If lights are on and fans are spinning when it powers up, but there's no video. Could be a loose screw shorting the mobo.

 

[Mictlantecuhtli]

the psu makes some sort of noise (not the fan)

Buzzing PSU usually means a short circuit somewhere. Sometimes the coils buzz a bit too, that's normal, but it shouldn't be clearly audible.

Sounds odd though that it just stopped working like that.

 

[R6MAD]

Try to turn off the PSU at the switch on the back off the computer for about a minute then try to switch on if that doesnt work get a new PSU