PLZ HELP I NEED HELP WITH MY DISK Management

ok im am running ACER ASPIRE 4520 windows vista.
i go to control panel->administrative tools->computer management->and on the left side diskmanagement-> i go there and nothing is there this is suposed to b the hard drives (im on a labtop) C: D: and the removeable ones but nothing is there it blank i need help to fix that or another way to to make things i install go to D drive(data) instead of C: Drive (local) plz i need help