Windows NT Profiles

Answer:
The following is from the MSDN article Q185588, "Guide To Windows NT 4.0 Profiles and Policies (Part 3 of 6)":

"Should multiple users with the same account name log on to the network, separate distinct profiles are created for each. For example, if multiple users with the account name John Smith log on to the computer, the first John Smith is assigned a folder named JohnSmith. Subsequent users with the same name are assigned folders named JohnSmith with a numerical suffix appended, for example JohnSmith.000, JohnSmith.001, and so forth."