Could it be as simple as windows just not assigning the USB stick a drive letter?
Go into Administrative Tools and select Computer Management. In Computer Management select (left pane) Disk Management.
When Disk Management opens it will list all the attached drives and the Drive Letters assigned to each.
Is the USB Stick listed, but no drive letter assigned? If so, right click on the USB Stick and select Change drive letter.
If the USB Stick does not show up under disk management, then other tools will be required, such as a third party partition manager.