unable to copy anything to my pen drive from my laptop , showing write protected

i have ASPIRE V3-571G acer laptop . when i insert any pendrive and try to copy laptop contents to the pendrive , then a write protected msg comes up . i am really ***** off . i am also unable to delete the pen drive contents . AND  the same pendrive when i insert to any of my frnds laptop , it runs very well . please help.