Permission Exception thrown while accessing a network file from a web service.

Hello Experts,

I am trying to re-write an existing web application as a web service. The application needs to access files that reside on
another computer within our network (through a mapped drive),therefore we are using Impersonation to grant
permissions to the aspnet_wp.exe process.


The Web App works fine, but within the web Service, a permission exception is thrown at second line of the following code:
(note: the web service resides on the same machine that the web app resides on.)


string path = @"E:\Images\Image1.jpg";
System.Drawing.Image myImage = System.Drawing.Image.FromFile(path);


(if I copy the file to my local C: and then try to access it through the web service, it works perfectly)

string path = @"C:\Images\Image1.jpg";
System.Drawing.Image myImage = System.Drawing.Image.FromFile(path);


In an attempt to see why it is working in an aspx page, but not in a web service, I tried to see exactly what
was being impersonated in the web app and the web service by using the following code:

string strUser = User.Identity.Name;

in the Web app, strUser is equal to the username that I use to log onto my machine.
however, in the Web Service, strUser is equal to an empty string, I'm not sure why this is.

Can someone please tell me why User.Identity.Name returns an empty string in the web service,
and help me solve this permissions dilemma.

Thanks in advance,
MAI