unknown folders in the Winnt directory

I have noticed random folders on our NT 4.0 workstations. Different machines may have a different number of these folders, but they are showing up and have nothing in them. They are in:
C:\winnt
and they all have folder names of:
~~ss(followed bya random number)
example: \~~ss12df -or- \~~ss5032
if anyone knows what is creating these I would appreciate it…