|Hi Dgb, expanding on T-R-A's reply.|
If the cmos battery has failed, the bios may revert to its default settings, which include the hard disk parameters. Thus the hard disk can no longer be accessed.
To test this, on starting the pc, enter the bios setup, and input the parameters.
Hopefully the pc should then be able to access the hard disk and load.
Sometimes, there is more than one set of parameters available for a disk, and
you may need to experiment
Generally the parameters are given are on the hard disk label.
As a matter of interest, where are you based? I am in Hammersmith, West London.
Good luck - Keep us posted.