1. Go to the server that manages your domain, and use Explorer to open the folder where the
user's roaming profiles are stored (usually %SystemRoot%Profiles[username]).
2. Select a user's folder, right-click on it, then select Properties | Sharing.
3. Share out the folder, and under User Limit select "Allow this number of users:" and set the value to 1.
4. Then click Permissions, remove access for all users, and then add access for only the user in question.
This only allows one connection at a time to the profile folder, which means that a user cannot log on to the same server twice.
One advantage of doing it this way is that you can select which users to enforce this on. Downside: If you have a lot of users in your LAN, this could be tedious to set up.
This was first published in July 2006