What you have to do is reinstall the password secure software that was on your pen drive so you can access your secure files again.
You can find the applications for Imation's flash drives here:
Just download it, then run the file and make sure you have the drive plugged into the computer.
Make sure you download the software for the flash drive you have, since there are different models on that web site. For additional information contact Imation at 1-800-351-8186 or email them to [email protected]