Looking for a program

I run a computer lab at a large community college. In the beginning of the fall semester we wish to have student and community member logon to the computers. We want a program that will block access if they don’t have an account and will that track which computer they are logged on to and the date, time and length of their usage. All machines will be Windows 98 and upgrading to 2000 or NT workstation is out. Our servers are strictly NT. Does anyone know of a program that we can use to do this?