how can I view a file which requests for password?

Odds are the email or webpage that directed you to the dowload presents the password necessary to open the file. If not, a wide variety of password-cracking applications are available; any which work reliably will cost you, and the better they work, the more they cost. Odds are you prolly really don't wanna open that file anyway; that setup is a favorite of folks who just wanna infect your machine with something pretty irritating, frustratingly inconvenient, and tediously tricky to recover from.