I've tried to convert my FAT32 drive to NTFS but eventually got the message: 'the conversion failed' (I tried it twice - same result).

If this fails to do the trick then you might be looking at a clean reinstall of you old system or Win10 as long as you have of the install media, keys, and above all your data. Since your not going to work on this until Monday maybe some of the other folks could give their opinions. Then follow up by looking for and deleting any of the folders noted in the Apple article that might still be present just to be safe. Be sure to back up your music just in case. What might be a good strategy is to use CCleaner to remove all the Apple software in this order: iTunes, Apple Software Update, Apple Mobil Device Support, iCloud (if present), Mobil Me (if present, nut not likely) Bonjour, and Apple Application Support both 32 and 64 bit. Read the second box and especially note 2. Thanks again for all the help.I think that CCleaner is your best bet but you should take a look at this Apple support info at Should that work? But I've had enough for today! I probably won't be able to get back to this till Monday. If that fails I could use CCleaner to uninstall all the itunes stuff (hopefully except the files) and then install iTunes completely new. I'll try Halasz's idea of using CCleaner to find the proper path for the msi file, and try putting it there.

I also tried the Apple update in Safe Mode but that didn't work either.

What is revert on itunes