Try to use disk management tool.

1. Right click on My computer->select Manage->select Disk management
2. There, select your pendrive from the deice list on the right side
Right click on it and try to format or create a partition. Just try and see whether it helps or not. But can't guarantee because I'm not using Windows.
Do it as administrator.
Tharaka
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Life is pleasant. Death is peaceful. It's the transition that's troublesome.