hi,
have you tried using the Pen Drive on another computer?
If you have and it is also not working, it means that most probably there is some problem with the Pen Drive.... you might want to look for your warranty card for a replacement....
if it is working on another PC, you might want to check that the USB drivers are correctly installed on the computer before trying again.... Also, you can try installing the drivers that comes with the Pen drive onto your computer and try again.....
hope this helps.....