511581-0201
Pendrive is not being detected

I have bought this 4GB pendrive on 29/8/08. And it is not been damaged physically whatsoever. Whenever I put it in my USB slot, it shows removable disk but it does not open it. If I click on to its sign to open it, it tells me to insert a pendrive. I wish you could help me out here with my new pendrive

Thanking you.