My external harddrive has turn into Local Disk and the computer will be hang.Pls Help ASAP

My external Harddisk My passport red colour has become local disk in “My Computer” and cannot open it in the “My computer”.This problem is since yesterday.What should i do to get the portable harddisk can use it again.I even cant format the external harddrive.What happen actually ??? Do i need to claim warranty for it?

URGENT !!! URGENT !!! URGENT !!! Need my file for school project

Try connecting the Passport to another computer, also run the DLG test to verify if it has any hardware problem. Click on the link for the steps to run DLG.