SATA 500 Gb on an ASUS K8V

I'm going spare. Seriously this is driving me up the wall to the point where i wish I'd never started with it.

To cut to the chase, I built my own PC with bits and bobs I had lying around and a rudimentary knowledge of legacy PC systems (circa windows 95/98).
I cannot get my PC to detect the SATA hard disk at all. I can hear it spinning up, but no life in it otherwise.
It's a no show on bios and doesn't appear if I run it with an IDE hard disk with the operating system on that to load up.

I've been ripping whats left of my hair out for months now and I don't know what to try now.

This is just one of the plethora of issues that have arrived since my endeavour.

I beseech you, oh Gurus of Geekdom. Enlighten me, sage ones.

Its a maxtor diamondmax22 500 gig hd. PC running XP sp3 and an ASUS k8v board. Not exactly lightning spec, but the board has a sata plug so thats why I got the kit. Any help appreciated.

Stuart.