Thanks for the reply. I had this application in mind but was not sure. I need a simple application which should ask for password whenever the hard drive is inserted in any machine. So will true crypt help me in this or any other application. I do not need to encrypt the data. So do give me your suggestion.
I don't know of any software that ONLY passwords the drive. TrueCrypt will encrypt the entire drive, so if that's not what you want, this won't work for you. It should however ask for a password before giving access to the drive.
No data stored on an encrypted volume can be read (decrypted) without using the correct password/keyfile(s) or correct encryption keys. Entire file system is encrypted (e.g., file names, folder names, contents of every file, free space, meta data, etc).