Set a Harddisk password

Hello,
Can any one advice me !!! I have a external harddisk , I want to put security to that , Like as a Scandisk Cruzer Flash Drive. If we insert that harddisk it will prompt for password to start in any computer . I want like this , please advice me is there any software will support or we have to do any settings

The above question has been already raised by srinivasu, but as required the safware solution for the question works on folders, but how to set to ask for the password when the external harddisk is connected to laptop ?

Please help on this

Prasad