PC won't power up with hard disks connected

[smogo]

I've just built a PC using:

Foxconn A74ML-K motherboard
AMD Triple Core Phenom X3 8400 2100MHz CPU
2GB DDR2 800MHz memory

It boots and POSTs fine... until I connect a hard drive to the power supply, at which point the PC will switch on for 1-5 seconds and then switch itself off. I've tried 5 different drives, both ATA and SATA, and it won't work with any of them... although it will work with a DVD drive connected.

It's also being a bit temperamental with a Radeon HD5450 graphics card; sometimes it won't stay switched on until I've removed that as well.

The only component that's not brand new is the power supply, which is a 450W model with 20-pin and 4-pin connectors. The motherboard's manual recommends using one with 24-pin and 4-pin connectors. Does it sound as though I need to replace the power supply, or is there something else going on? There are no beep codes at any point.

Ta
Cliff

I've got a 450W power supply.

 

[COLGeek]

It sounds like a defective PSU. Time for a new one. What is your budget?

 

[smogo]

Thanks, I just wish I had a spare I could use to test out before I splash the cash! Oh well....

 

[mhokett]

try to pick one up from a local store so you can return it if that doesn't fix your problem. either best buy or frys comes to mind.

 

[Onus]

If you go to Best Buy, avoid their Dynex and Huntkey/Rocketfish PSU-shaped objects. Many of the latter burned during testing at HardwareSecrets, and the former received a particularly scathing review over at HardOCP. Fortunately, you should be able to find Antec and/or Corsair there. They'll make you pay through the nose, but a cheap PSU is never a good choice.