Using files on other server

Hi,
trying to get at Access db held outside of the server running IIS & .NET but appears that web app doesn't have permission to access with read/write the remote files & directories for access db's and mdw.
HOwever, the user that the .NET stuff uses cannot be given permissions being only in the domain of the IIS server.
Tried setting to account on the other domain - but not sure if did it properly or if this other account doesn't have enough privilidges to access the stuff under the web app's dir.
Please could someone explain what approach I should take.

Thanks in advance.