Thanks for pointing me in the right direction turingtest2, my iTunes software is now up and running.
Followed instruction in the 'second box' you mentioned (seems a bit obvious now) and installed iTune version 11.1.5.5
as provided by and suggested by Apple for Windows XP 32bit machines.
iTunes then started up but reported that: -
'The file 'iTunes Library.itl' cannot be read because it was created with a newer version of iTunes'.
which made sense as the attempt to run version 12.1 would likely have written a newer file into My Documents/My Music/itunes/ directory which version 11.1.5.5 would not know about.
The /My Music/iTune directory remains unchanged following the uninstallation of iTunes. If I understand correctly on startup, Itunes looks for and reads the file 'iTune Library.itl' to locate your music. When reverting to an older version of iTunes, this file now confuses the software.
Fixing this problem is well covered on the internet so followed the instructions. Essentially replacing my current version of the 'iTunes Library.itl' file located in your /My Music/iTunes/ directory with a copy of a suitable historic file named 'iTunes Library' (date stamped) from /My Music/iTunes/Previous Libraries directory. (The files in this directory are date stamped for example iTunes Library 2014-12-24) choose the most likely file in the list that you know was generated when iTunes last worked correctly. This is likely to be the last file in the list. Move it into /My Music/iTunes/ directory changing its name to 'iTunes Library.itl'. You should keep a copy of the existing 'iTunes Libraery.itl' maybe on your Desktop first, just in case!
At this point restating iTune prompted me with the option to look for and import 'media' which I said yes to. iTunes then started listing all my music as it was imported into iTunes. After a minute or so I noticed that photo images from a completely separate directory seem to be being imported so I stopped the importing. Restarted iTunes and all my music appeared as before. What happened to the photo images that I I don't want in iTunes that appeared to have been imported, I do not know.
Interestingly when first plugging in my iPod iTunes claimed that it required a Factory Rest which would trash all the music on it. I declined this option. Unplugged the iPod, restarted iTunes and plugged in the iP{od a second time, now read correctly and all OK.
Might just mention that on this PC I have two other iTunes accounts used by other members of the family. In these accounts I could not find an 'iTunes Library.itl' file, only one named 'iTunes Library'. So when I copy the 'iTunes Library (dated) file, I just named it iTunes Library. All seems OK with these accounts.
What a faff for no gain.
Thanks again.