ASP.net Getting the error “Access to the path is denied.” while trying to upload files to my Windows Server 2008 R2 Web server

I have an asp.net webapplication that uploads files to a specific folder on the Web server. locally everything works fine, but when I deploy the application to the Webserver, I begin getting the error “Access to the path “D:Attachmentsmyfile.doc” is denied”. I gave the “IIS AppPool” user that the application is running under full permission on the folder. I even gave “Everyone” full permissions, but with the same error.