How to share directories on boot partition?

I have a clean Windows 7 install on the c: partition. I want to share some
of the directories on this partiontion. I set up sharing just like I set up
sharing of directories on other partitions. All shares on other partitions
work fine, but I am unable to access any shares on the c: partition. Is
this some sort of weird Windows 7 restriction? Is there something special I
have to do to share directories on the boot partition? I am trying to
access these shares from boxes running WindowsXP and linux - they all get
permission denied errors.

On 17 Sep 2010, Zootal wrote in
alt.windows7.general:

I set up sharing just like I set up sharing of directories on
other partitions.

And how is that?