Bios SATA 1 device not detected

Recommended by Wim's BIOS...

Hey I just bought a new computer recently and having some problems. It was working fine and then I shut it down and then it came up the the error "reboot and select proper boot device". I wasent tampering with anything it just randomly came up with this message.

I went into Bios (v02.61) American Megatrends and the SATA 1 device was not detected. BIOS is not detecting my hard drive for some reason. It detetcs my DVD player in SATA 2 but every other SATA slot is empty. I tried to make sure the wires were in correctly and they were but that didnt solve my problem. I know the hard drive is spinning because I could hear it. There was also some message regarding express gate but I dont know if thats part of this problem. IS there some setting in the BIOS to the hard drive bootable? I should also add that suring start up before it never recongnized the hard drive but it booted up still.

My system specs:
Quad core Q6600
DDR2 memory 4 gigs
ASUS P5Q SE motherboard
Nvidia 9800 GT video card
Vista home premium 32 bit
Seagate 500GB hard drive

Thanks

[edwin]

It was working fine and then I shut it down

shut it down how?

make sure both the power cable and the data cable are fitted properly on the harddisk.
power up, go into cmos setup (I think by F2), clear cmos by setting it to defaults, save settings and exit. This should get you back on track.