Access to network drive through webpart is denied

[Indo77]

I have big problems running a webpart in Sharepoint that will allow a student access to their network drive from outside the college. The problem is not with the code, but either permissions or the web.config file. When I test the script out on my development machine, it works fine and accesses the network drive, based on my Windows login information. However this is not the case with Sharepoint. I have tried everything from <idenity impersonate="true"> to giving full permissions on the ASPNET and Network Service accounts within Windows Server 2003. Can anyone suggest where I should go with this?