I'm desparate now, having to reply to my own message!
Would it be too much to ask to have an Adobe technician explain why this is happening? Is there any chance of this being put right or have I got to convert all my pdf files to something which does work with Windows and chucking Acrobat in the bin?
I can't say for sure, it might be an issue with Explorer.
I would advise you try using Adobe Bridge to browse through your PDFs. It will allow you to look at the Title and many other metadata. You should have it installed on your computer if you have Acrobat.
Acrobat, as a point product, does not include Bridge.
You can get Bridge as a point product, as part of Creative Cloud, or a Creative Suite.
I ran into this too and it drove me crazy. After much google searching I ran across PDF-XChange Viewer from Tracker Software. After installing this PDF viewer, my titles appeared once again in Windows explorer.
I found that the free version was enough to solve the problem.
But I still believe Microsoft and Adobe really need to get together and solve this because the loss of this feature when moving from XP to Windows 7 is significant - especially in the business world where we make extensive use of PDF files.