Help .. help.. when i open my pendrive, all my data is missing, but the space is still in use.

Question

when i open my pendrive, all my data is missing, but the space is still in use. what should i do? it only appear something like thisWMP info and when i click it straight goes to tihs msg <WMP DeviceID="{1FA765E3-000E-4C39-A7C6-23FBE66B8388}" RelationshipID="{00000000-0000-0000-0000-000000000000}" />