New build, boot issues

Hey again all

Earlier on today I finally finished building my new rig, and after trying to use the overclocking software on my Asus Maximus II Formula I've hit a few snags

Firstly it told me I needed to restart, so I let it. Then it didn't reboot.

Then it told me that the overclocking procedure had failed on the bios as it booted, and I could load with standard settings which I thought great I'll do that.

Now everytime I reboot it says operating system is missing!! One thing that had been bothering me was just how often the HDD seemed to be accessing itself, about 90% of the time so it was far from quiet.

I'm currently waiting on Windows Memory Diagnostic Tool as I type this up on my laptop.

Any ideas? I've got this horrid feeling it might well be one of my new Samsung Spinpoint HDDs

If so I've lost a large chunk of data I moved across, stupidly moving it instead of copying it as I wanted to free up some space on my USB HDD.

The rig as mentioned earlier.

Motherboard: Asus Maximus II Formula
Gfx Card: Zotac 8800 gt Amp
Processor: q6600
Case: Antec 900
HDDs: 2 500gig Samsung Spinpoints
Optical: Samsung DVDR
PSU: Be quiet 650w modular PSU