The only thing that I always see what people do is that they cannot set permissions for this resource. To set up a shared folder, you must do the following:
1) Define the account under which you will connect to the shared folder 2) Grant access rights to the account in the file system
3) Grant this account access rights to the shared network file
No. 1, in this case usually means checking your configuration or just using the process explorer to determine which ASP.NET account is running. Lots of google info on how to do this.
No. 2 is obvious. You register on the machine where the physical disk is located, find the folder in Explorer, right-click on it and go to the security tab. We have done this several times.
No. 3, where people are messy. Yes, the work account now has rights to the local file system, but not to CONNECT to the local file system over the network. On the Security tab, go to the network sharing tab and find the Permissions button. You will use this to provide workstation accounts with a connection to a shared resource.
The second problem I saw is when people try to grant access rights on machine A to an account that exists only on machine B. This will not work at all. Both machine A and machine B must belong to a common domain that A and B trust for user authentication. Most often, enterprises running Windows use ActiveDomain to control access rights on the network.
For an ASP.NET workflow on computer B to gain access to a resource on computer A, the workflow must be performed under an account that is authenticated on the network, and not just on the local machine. Most often, you will have to create a specific account on the network and grant account rights to both machines, and then use this account to start the ASP.NET workflow for your site.
If you scratch your head, you need to learn. It's not easy. I highly recommend reading the following:
http://msdn.microsoft.com/en-us/library/ms978378.aspx
Its relatively clear and contains everything you need to know.