Tortoise Bug: Windows(Vista) mounted NTFS partition not usuable (not regocnized as directory)

First apologies, for I have done this the wrong way round and reported
it already (http://subversion.tigris.org/issues/show_bug.cgi?id=3604).

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On Windows(Vista) it is possible to mount a partition (partition on the 
local / build-in drive) as a folder, instead of assigning it a drive letter.
In my setup I partitioned the build-in harddisk, making 2 partitions:
partition 1 has the drive-letter C:
partition 2 is mounted as C:\data  (C:\data has to be created as empty 
folder first, then the partition can be mounted)
If I try to checkout (new checkout) of a repository into C:\data I get:
- A warning which is correct:
   the folder is not empty (because there are some system folders, such 
as volume-info and recycle bin).
   I confirm that I still want to continue and this does work
- An error (which I believe to be a bug)
    C:\data' already exists and is not a directory
Similar if I copy (including hidden .svn folders) an existing checked 
out repository into C:\data some svn function (such as update or log) do 
no longer work (they still work on individual sub directories).
If you try "show log" on a repository copied into such a folder, 
tortoise claims "'C:' is not a working copy" => despite executing the 
command on "C:\data" (again subfolders in c:\data (that are part of the 
checkout) do work
Best Regards
Martin