How can I change a drive icon in Explorer

So I have a little time on my hands over the Xmas holiday. )

I decided that I needed to change the icon that explorer uses for my
external disk drive.

My old XP PC used to display it correctly using an icon that came on the
driver CD

I did the REGEDIT thing;

I created the following key and pointed it at the 3dhdd.ico file

[HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Explorer\DriveIcons\C\DefaultIcon]

It didn't work! I had a look at some other icon files in Vista and they were
different so I used IcoFX to create a Vista compatible icon file containing
four images, a 256x256 True colour, 48x48, 32x32 and 16x16 this was saved as
a new file extDrive.ico

Now when I click on computer in explorer I see the new icon complete with
the bar showing used and free space.

My problem is that the small icon in the navigation panel on the left where
all the drives are listed is displayed as an empty white square rather than
the small icon I'm expecting to see. The details pane at the bottom of
explorer also shows the correct icon, and very pretty it is too.

Have I missed something?

Have I done something wrong?

I'm 95% there. Can anyone help me sort this out please?

Happy New Year.
--
Regards
Nick