bios won't detect hard drive

[Mick_D]

My problem started with a computer that power was dead except for the led light on the power switch. The psu fan was not running as well as the case cooling fans. I replaced the psu and reseated the cpu, ram, and video as I was going through the barebones boot one item at a time. After reseating the cpu I was able to access system bios. All seems to be working fine except I cannot get the bios to recognize my hard drive and therfore no boot to OS. Any ideas please.

System specs:
Mobo- DFI Lanparty pro 875B
CPU- intel 2.8 ghz P4
PSU- antec 550 W (dead psu 420 W Thermaltake )
RAM- 1.5 gig PC3200 DDR Crucial
Vid- Radeon 9800 pro 256 mg

[jsekasi]

have you tried advanced bios setup?, if auto detection in the bios doesnt work,then try configuring it mananualy and see if the bios can detect it

[Mick_D]

Yes I have tried the advanced bios setup in auto detect and manually entered the HD config data in the bios and still get the message "boot disk failure" when trying to boot. I have reseated and replaced all connections to the HD and the MOBO.

My questions more relate to why a PSU failure would cause a CPU to be taken out and reseated to get the computer to post?
And also what could tie the loss of HD detection in bios to the PSU failure?

I can continue with proceedures to boot from XP Pro CD but I am questioning what happened to the system bios after the PSU failure?