Thanks once again to everyone who has responded. I think I have now achieved what I set out to do which I now summarise here for anyone else who might be interested (in the hope that it may save them a lot of grief at some time in the future).
I have no doubt there are other backup programmes, but I have used Take Two from Adaptec which is included with Adaptec Easy CD Creator Version 4 Deluxe (thanks for that pointer spannersatcx). This writes a compressed disk image to CD under Windows (ideally this should be done under DOS to ensure that there are no files open - but Take Two checks to see what files are actually open and judges whether they are significant or not). This suits me because I don't want (large) backup files cluttering my hard disks until I actually need them. It's a very easy three step process with Take Two and a DOS boot/recovery diskette is created the first time you do the backup.
My laptop (with about 500Mb on the hard disk) compresses down to about 180Mb, and my desktop (2.62Gb) compresses down to 1.6Gb and spans 4 CD-R/W disks (493Mb/disk). The desktop took 2 hours 17 minutes to write the to the disks (so it's probably not something I will do every night).
Unfortunately (Ironguts) there are no "real mode drivers" for the HP CD Writer (I checked directly with HP).
My recovery strategy is based on the assumption that only one machine will crash at one time (if both get smashed I'll have to do some more thinking).
If desktop crashes, attach CD Writer to laptop; Bring desktop up under DOS; Use old DOS version of LapLink in DOS box to get backup files across to desktop, and the proceed with recovery.
If laptop crashes, reverse the procedure to get backup file across from desktop to laptop.
This does mean that I need to ensure that there is enough disk space for the backup file and the recovered files (particularly on the laptop which only has limited hard disk), but should be enable to ensure this will be the case by only backing up a "bare bones" operating system and application packages (ie. without any data files) and maintaining a backup of the data files elsewhere.
This is not quite as simple or elegant as I had hoped, but at least it should get me back into business without having to completely re-load everything (which is, at best, a tedious process).
Whatever backup software is used, recovery will rely on the machine being recovered recognising all the necessay disks when bought up under DOS (ie. it may not recognise devices (such as a CD Writer) attached via parallel port or PCMCIA card). Also, the actual backup files themselves must be named according to DOS naming convention (8 letter name with 3 letter extension).
Hope that may help some of you out there.
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Feline
(I Sit, I Watch, I Smile)