Outlook Express writing files to Root Drive?

I have come upon something I have never seen before on my boss's laptop. Seems like whenever he opens Outlook Express to check his personal email it writes a file to c:\ that starts with an "S" and normally a 2 code extension such as: s3ho.2n, s3b4.1f, s7f9.28, etc... there were THOUSANDS of these files on his root dir. If i open any of these files its just the text version of all his emails. Has anyone ever seen this and know what is going on? I've run A/V scan daily on his laptop (norton corp 9). I'm at a lose and cant find anything on the web about it.

please see this screen print for more info:
http://www.pyehl.com/Keith_OutlookExpress.jpg