Some times our computer do not obey us and do not want to detect mass storage device.At that time just treat it this way,,
1.Open device manager (if by run terminal than type devmgmt.msc)
or directly right click on my computer and choose manage
-on that select device manager
2.Go to universal serial bus controller
3.Select mass storage and through right click on it uninstall it.
4.Restart your computer
5.Now ur computer will automatically install device driver software for it
Best of luck
