gone to switch on pc today and screen come on and says boot disk required and it wont boot up at all? any ideas please.

Your computer is telling you the operating system cannot be found.

This might mean a corrupt file (MBR possibly) or the disk itself has developed a fault.

(assuming ur on WinXP) If you have a windows CD, boot from that, get to the recovery console (it will tell you which buttons to press) and try running chkdisk.

There are options to give chkdisk to automatically repair things, but if drive is failing then this wont help. It will at least confirm one way or the other.

it may be even a bios fault, make sure it's seeing the hard disk in the bios, if it dose then you need to see if the PC is set to boot from it. i'd do that 1st before committing to formatting.