usb external drives on a R7500

The router firmware version is V1.0.0.94 and my Windows version is Win7 Professional. The way I would map the first usb drive is as follows: Windows Start button > Computer > Map network drive (from Tool bar) > Drive: Z > Folder: \\192.168.1.1\USB_Storage > Finish.
I followed simular steps to map the second usb drive but my mistake was to guess the //server/share name, which was always incorrect.

I finally got it to map the second usb drive with the following steps:

Windows Start button > Computer > Map network drive (from Tool bar) > Drive: x > Folder: \\192.168.1.1 > Browse... [which then showed my share name choices as \USB_Storage or \USB_Storage(T)]. When I selected \USB_Storage(T) > Finish I was successfully able to map my second usb drive and access it simultaneously with the first.

If I clicked on Browse... with the //server/share name blank, it did not show any choices. It was not until I typed the //server name of //192.168.1.1 and then clicked on Browse... that I was able to see the distinction of the two /share names.