System wont boot with 2 or more HDDs connected

Hi Guys

I have *** very annoying problem that i was hoping for some help on.

I have just built myself *** new RIG, by taking parts from my old rig and *** couple of new parts. On my old PC i had 3 HDDS connected internally and 2 HDDs externally, everything was working fine.

I have now built my newer build, and i can boot and run windows 7 perfectly, only if i have one hard drive connected.

As soon as i attach another, internally, BIOS will not boot from the Hard drive. It recognises both hdds, but will only let me boot from the hard drive without the boot files on it. Obviously this is annoying, and i don't want to have to invest in 3 extra HDD cases and *** multi-tap to be able to use all of my space.

I have been reading up on things, and one thing i was unclear on was whether the drives are master or slave drives, which could affect the boot process.

How can i tell whether *** hard drive is master/slave, and how do i change these settings?

Are there any other things that you guys can think of that would enable me to run my pc with all 3 internal hdds working?

Spec:

4x2gb DDR2 Kingston Hyperx @ 1066mhz
Intel Core 2 Quad Q6600 @ 2.4ghz
Asus P5Q Pro Turbo - Atx - LGA775
Windows 7 Ultimate x 64
3 x seagate barracuda 500gb @7200rpm
2x seagate barracuda 1tb @ 7200rpm.
OCZ 600w Stealth 2 Extreme PSU
Gainward GTS 250 1024mb Gddr3

Many thanks in advance

Serth