Actually, never mind all that, this post on another site nails it exactly. Try:
http://www.technipages.com/itunes-fix-iphone-or-ipod-not-detected-in-windows-8
It will also work on windows 7. In case the link is broken what you do is:
- Open devices and printers, you should see the ipod in 'Unspecified' if it isn't there check the connecting lead is supported.
- Right click and select properties, then hardware tab, properties again, then general tab, Change settings (blue/yellow shield thingy)
- Next popup, select Driver tab and update driver
- Select Browse my computer for driver software and navigate to:
C:\Program Files\Common Files\Apple\Mobile Device Support\Drivers. If you don’t have this folder, check in C:\Program Files (x86)\Common Files\Apple\Mobile Device Support\Drivers.
Fantastic! Thank god for support communities, and thanks to Mitch Bartlett for posting the solution.