I can also see all my other partitions from "7". But I am not sure when this occured as I have been customising heavily (again!).
The only reason they are invisible, I believe, is because they have not been allocated letter designates. Thsi was once mentioned in a Microsoft comment as ththeir new reccomendation to give names to aprtitions rather than hard disk letters. Follwing that policy, I would now describe this as a "bug" in "7" and have posted as such.
To regain sight of the other partitions, I went to Disk management and gave the other partitions letters (They were all visible under disk management). They were then again visible in the Windows Explorer.
It would be interesting, however, to know if Ex-Brit's other partitions were visible from installation?
Fwiw. I think that is a wise precation, Ex-Brit, I don't think the fact that they are invisible, neccessarily means they cannot be accessed by "7".