Windows failed to load because of kernel missing or corrupted

Hi

I have an INSPIRON 640m which has stopped working (without any previous signs of things going wrong). The message on start-up is

Info: Windows failed to load because the kernel is missing or corrupt

Status: 0xc0000011

\windows\system32\ntkrnlpa.exe

The diagnostic tools don't find any hardware faults, but I haven't had any success in getting the recovery disks to boot. It was originally an XP machine, but I upgraded to Vista with the disks from Dell as soon as Vista was released.

Can anyone offer any clues as to what the fault is and where to go from here?

Thanks

Rob.