User automatically logs off

[Matthew Lamb]

I have a windows xp pro machine setup in my parts
department to receive faxed orders. It will not receive
the fax unless it is sitting at a desktop screen (not at
the login screen, even when a user is "logged on")

The problem is, the Parts department user logon keeps
logging off automatically after 30 mins or so. How can I
disable this so it stays logged in indefinately?

Thanks
Matthew