Right-click the file in Explorer, choose "Properties" and select the Security tab. Click "Add" to add the appropriate user or group. Highlight the ASP.NET account, and check the boxes for the desired access.
In case there are lots of file or more files are to be added in future. Consider giving rights on folder.
You can also try running ASP.Net from Admin account but that will pose security threat.
Thanks, Durgesh Chaudhary. http://home.techphernalia.com