Thank you for the link to your ppt.
Meanwhile it was very interesting for me concerning some other "mysteries",
I still cannot create a texture using D3DPOOL_MANAGED.
Vista Enterprise SP1 and latest ATI driver (2008-08-01) is running.

The reason for my efforts:
So far I mainly used D3DPOOL_DEFAULT for allocation of texture memory. As
textures have to be loaded dynamically, I backed them with a plain surface
in D3DPOOL_SYSTEMMEM. When preparation of the texture in this surface was
completed, the transfer to the texture was done by UpdateSurface().
This runs with good performance under XP, but using Vista the memory access
to the plain surface is rather slow. A memcpy of 12 megabytes from
application allocated RAM to the surface takes about 20ms. For this reason,
I wanted to give Managed Textures a try.
What else could be done in order to quickly change the texture's content?

Thank you in advance!

P.S. I just found out that if I create a Direct3D9 object (instead of
Direct3D9Ex as I do now when Vista is recognized), managed textures work
fine. But they don't seem to solve the problem that an update of the texture
is significantly more time consuming than using good old XP.