Sophos Temp files filling drive?

I have a user who is complaining that his disk keeps filling up. In checking for what is eating the space we find a directory at C:\Documents and Settings\All Users\Application Data\Sophos Anti-Virus\Temp that is filled to the brim (11GB) with files ending in .$$$. These files range in size from 12MB to 2.8GB in size. I would like to know what these are and how to keep them from filling up this drive!

Thanks in advance!