I’m pretty sure you may have come across the error ‘Problem ejecting USB Mass Storage Device’ while trying to eject your pen drive. And, since you couldn’t do anything you simply pulled it out. Well, the reason for this problem is that there’s a hidden process or some malware activity which is restricting the pen drive from being unplugged.
I came across a tool known as LockHunter. It is useful for fighting against malware, and other programs that are blocking files without a reason. Unlike other similar tools it deletes files into the recycle bin so you may restore them if deleted by mistake.This tool can help you to find hidden processes and kill them. Once you do that you can eject your pen drive without any probs.
-Shows processes locking a file or folder
-Allows to unlock, delete, copy or rename a locked file
-Allows to kill locking process
-Allows to remove locking processes from hard drive
-Integrates in to Explorer menu
-It deletes files into the recycle bin, so you may restore them if deleted by mistake
-Supports both 32 and 64bit Windows