Cannot extend sub folders in sharepoint 2013

Question

I've created a web application in visual studio 2012 then i deployed in SharePoint 2013 using master page now in that i have upload document button if i click that it will show for browse folder and destination folder if i click  destination folder and  enter some drive name it will show the folders in that drive but its not showing subfolders if i put C and D drive its showing i guess mapped drives not working properly can any one suggest me how to solve this issue. Thanks