Seasons Greetings

Have a real strange one

PC intermitently won't boot at all when it does get message boot disc failure insert system disc.

Have tried swapping a known good HDD but get same message. Also took voltage readings and both 12 and 5v rails are reading twice what they should (24/25v and 10.6v).

Swapped known good psu and still getting same readings.

Any help greatly appreciated.

Thanks in advance