i have a problem with my external hard disk wd 500gb, one day unknowingly i change security option of my hard disk in windows 7 from that day my hard disk is not accessible in other computers having any operating systems.
just connect your HDD & select properties
then in security tab
select "EVERYONE" --> then edit (you must have admin rights in this pc to do this)
its will open new window,
select "EVERYONE" from first box & enable all the boxes under "ALLOW" then click apply.
it will take some time to apply new policy then you are done ...