It was just on a constant reboot cycle. It would go through the usual ram, hdd checks and just before you would expect to see it loading WHS, it would reboot.
I'm guessing either something is corrupted in the OS or the HDD with the OS installed has failed. I couldn't hear any unusual noises/clicking from any of the HDDs, so I though I would try to repair the installation by booting with the WHS install disk and going through the repair steps.
I opened the tower up, attached a dvd drive, changed the bios setup to boot from it 1st, but when it the 'Windows is loading files' screen appeared, it progressed about 1/20th of the progress bar and rebooted! And kept doing the same each time.
So, this is where I'm hoping for guidance so I don't mess up anything in trying to isolate the problem.
The machine comprises of 10 x 2TB drives and I'm not sure which has the OS installed on it - I installed all HDDs at once and loaded WHS - probably not the best idea. All HDDs were bought new and the systems has been running flawlessly since Nov 2010. It has a heap of Win MCE recordings on it along with iso copies of dvds and blurays.
Any logical steps to follow would be greatly appreciated!