Thanks everyone for the advice.
The present machine is a laptop, but I have encountered the problem before.
The problem drive is a seagate Momentus 40Gb IDE (Don't laugh) Model number : ST94Q11A
It seems the mbr gets physical damage and the recommendation from shops is always one of "replace". But - out here in the Sticks (South Africa) we try to fix before we replace. IDE drives cost the equivalent of half a new laptop these days. From there my enquiry.
Fzabkar: I do not suspect the ram, as replacement of the HDD results in a working machine.
Danny2000 : FixMBR yields no results.
Phil22 : Thanks - that at least answers one question I always wondered about. Pity though. Could have meant the resurrection of old drives.
Scout_03 and LP-90 Amazon refuses to ship to South Africa. They did books and CD's only for a while, but that has stopped as well. Buying over the internet is often a problem in South Africa as many people simply do not ship here. Which is why we try to fix before we buy.
Thank you everyone - I will try your suggestions and get back as soon as I have results.