Itunes not recognising Ipad

I have had an ipad 4 since Christmas 2012. I synced it with the laptop I had at the time, which was running Windows 7. Never had any problems. I had a new laptop last (2013) which runs Windows 8.1. (The old laptop still works.) I downloaded itunes, imported my library, added some extra music from CDs, Authorised the new laptop, unauthorised the old one, plug in my ipad. The computer recognises it (it show up in Windows explorer) but itunes hasn't detected it. I'm using the same itunes account. I have done allsorts of things suggested on here and other user forums - nothing. I've uninstalled/reinstalled itunes. - nothing. I've updated the ipad to IOS 7 - nothing. Can anybody please help me? I don't want to have to turn on the old laptop, just to sync my ipad!