security issue in UNIX

As UNIX provides the facility of MULTIPLE USER ACCES , how come it is more secure than WINDOWS which doesn't do the same????

any one plz help me out.. :)

here i explain in brief about security b/w windows and unix.
in windows the password is stored in encrypted manner.
when you type your password it decrypts the stored password and compare it with the one you just typed.
but in unix if you enter password it also encrypted and compared with the stored encrypted password.
so there is no way in unix to find the password but it is not in the case of windows.