PC Build Help, Boot Problem, Turns on cant go into BIOS (Asus)

Hi, Ive just 'built' a new pc with the ASUS M3N78-WM MB and turned it on, everything seems to be working fine, computer starts and the ASUS screen comes up, it says press TAB to go into BIOS or DEL for setup, neither seems to respond, the PC goes to a black screen saying;

'Reboot and select a proper boot device or Insert Boot Media'

Can someone please help, I am using an IDE DVD-Drive and a 1TB Sata HDD, both seem to be connected fine, power etc but i cant get past this screen, thanks

EDIT: I have finally figured out how to get into BIOS, (hitting the del key about 10 times)

For both my drives, it doesnt seem to detect (not detected), does anyone know what is the problem here??

 

I took a quick look around, saw a similar problem that I encountered with my new Gigabyte mobo at the weekend.

Try switching the AHCI in the bios to IDE emulation. It may not be relevant, but this is what I did to fix the same issue on a different mobo.

 

That message will be caused if the hard drives are either blank or they don't have an operating system installed.

If this bios isn't detecting them then are they connected to the motherboard? If they're connected to an expansion card then the BIOS won't care about them but your OS installer should still pick them up.