This is the 3rd time trying to post a reply to you and I'm hoping it gets through (you should have guessed this is a novice).
Thank you for your suggestions which helped solve my problem.
Neglected to mention I'd tried booting from the XP disks earlier but failed as the
Compaq had been reluctant to do so for about 6 months. However, someone on
the Net suggested removing the peripherals (in answer to another person's query).
I did this and managed to boot the disks and all is well.