There are a bunch of computers that I manage that are used by various people as dumb terminals that are connected to a server to hold their personal documents etc.  Due to the nature of the computers use I cannot just remove to ability for them to be able to install some programs and access to other things so eventually the computers get clogged with crap and then reimaged. This isnt a huge problem but I am wondering if the following is possible:

Have the computers automatically, periodically, reimage themselfs from an image held on the server so that say, once a week the computers would be reset to a defined state.  

Or if that seems to be an overkill and a better way would be to simply reverse any and all changes made to the machine on reboot then that would work too.

Are there any suggestions on how to go about doing either of these? preferably the reverse changes one as it would require much less network traffic..

Thanks