NT and Disk space per User

SpaceGuard is a disk space management tool specifically designed for Windows NT. With SpaceGuard, a network administrator can limit disk space for individual users and groups.
When users exceed their limit, both users and administrators are notified with pop-up and E-mail messages. If users ignore the messages SpaceGuard can revoke their write access privileges.

SpaceGuard helps administrators ensure that file systems run properly by monitoring and limiting disk space usage. Now, administrators can have full control over the amount of disk space available.

SpaceGuard is a client-server application. The service is a 32-bit multithreaded NT service that runs on each NT server with disk space to be guarded. The SpaceGuard client is a 32-bit application which runs on Windows 95 or Windows NT.

SpaceGuard Query tools are available to users to monitor their own disk space usage and limits.

SP4 for WinNT 4.0 contains an executable (PROQUOTA.EXE) that ensures a user's profile does not exceed a specified limit -- it prevents him/her from logging off -- but I think you'll be wanting something with a wider scope.

Quota Manager is third-party software from NTP Software, Inc. (www.ntpsoftware.com) that can help you. They also offer a 45-day trial on their website.

Argent Software Inc, of Torrington, Connecticut, offers Quota Server for Windows NT.

Something notable to mention,though maybe not an option for you, is that NTFS version 5 has quota managment built-in. Unfortunately, or maybe not, NTFS version 5 is only available with NT 2000.