Which shared folder a Domain User has access to

Are you trying to find EVERY share that may be accessed by a specific user?

Take a look at http://technet.microsoft.com/en-us/sysinternals/bb897332.aspx.

Also do a search for some vbscripts to do this, unless you just want to look at every share in AD manually.
 
Each thread in a computer runs under a specific user account. Shared folder have security settings, i.e. they are subject to ACL-based access control, so that some users may have access permission and others may not. This means that the thread in your program may be able to "see" some shared folders, while other threads in the same computer (including the interactive user using the desktop) might be unable to "see" those folders.

In summary: you should assume very little.

Lepide