Disk does not show up anymore

WD External Drives External Drives for PC
1

After installing windows 7 service pak,My book Essential does not show up anymore.

 

I  desperately  need help!!!

2

Did you try disconnecting the drive rebooting then reconnecting?

Joe

3

 Windows ask me to format my external drive in order to show it but I know there are original stuff on the disk and I am afraid to miss someting later (i.e. wizard)