thanks everyone, for those helpful ideas; I'll have a go tomorrow. And thanks Chubtor for the point aboutnot having the scanner plugged in ;I'd begun to wonder about that & had already decided t0 unplug before I attempted any further installing/uninstalling, etc, etc.

I have solved the problem –I went to the Canon site; clicked “Support” (or something like that) and after hunting through various lists I found a new software download that was appropriate for Windows Vista 32 (which is my system). I downloaded that & installed it- a simple process.

I very soon knew things were Ok because the scanner started to make it’s usual waking up noise. I’ve now done a test scan & everything is fine.

Google search produced something that I could not use as I didn't see what the writer of the advice saw! So I returned to Canon website to download the software again. It was impossible to work out exactly what I’d downloaded the first time so I chose something fairly much at random (8800 Fust1300ea24.exe in case it’s helpful to anyone!) and when that offered a list of several items I downloaded 2 of them & installed both. And now everything is as it always was - and I’ve taken the opportunity to delete some saved stuff that I no longer needed. So it's now fixed - at last ; and have used it several times – just to be sure. Sorry I can’t provide any more precise advice/info; it was all very hit& miss. Thank you everyone.