Try this 1
1) First follow the instructions given by "Saman.tha".
2) Right-click on your pen-drive --> Select the option "Explore" --> if is gets
opened, backup your data and format it.
If the problem still exists then
Click on Start --> Run --> Type diskmgmt.msc and click on OK.
Disk Management will be opened.
Then right-click on your pendrive ---> Select "Change Drive Letter and
Path.." --> Click on "Change" and assign different drive letter.
Change the volume name by right-clicking on your pendrive and select properties.
Enter your volume name.