MMC card that unvisible in your pc

my friend asked me about his N-gage memory card that become unvisible in his pc. he told me
that yesterday, when he wanted to transferred the data from his pc to his memory, suddwnly his
pc was turned off and when he started it from all oevr again his card become unvisible
(his pc cannot read the data from his memory). it is also can happen to flashdisk, when
we want to plug it in to our pc, sometimes it become blank. but dont worry.,
i have the solution for you, just follow this steps:

1. click my computer and choose properties-hardware-device manager
  then try to find your hard disk (disk driver) right click-scan hardware changes

2.for axehead.png flash disk or mmc that unwritten in your pc foollow this step
click my computer-choose manage-click disk management- right click then choose
change driver letter and part.-add-change-then choose the drive that youy want F.G,H

3.the last step, try to plug it in another pc. if it still dont work perhasps your memory
or flash disk was broken the solution is try to buy the new one.