I tried that originally Paul, and my first thought was that was the reason, it had to be in MS' specially constructed MSSQL (it doesn't actually, but being elsewhere requires a lot of other settings/permissions).

And I am administrator, so if I start with insufficient permissions, Windows 7 lets me add them when required.

As mentioned, I have also downloaded the OLTP database, I can't see anything different in the the two files or how I tried to attach them, but teh OLTP database attached perfectly, first time.