Sharepoint services 3 - user profiles?

[Oops_my_bad]

I've just been onto our sharepoint machine (which does our SIMS Learning Gateway) however when checking a few things I noticed there was a shed load of user profiles in the c:\users directory.

 

Now these appear to be users who would logon to the sharepoint site and would have no access to interactive logon - question is why are user profiles being created in c:\users for these users and how can it be stopped?

 

It's WSS3 running on Server 2008

 

Any ideas?

 

Cheers