Redirected my documents not to be synchronised

Hi guys,
I’ve set up a small-office 2003/XP network in which every user document folder must be redirected into a common share. I made an OU, applied a GP and all seemed okay. But…
Although alla the PCs are desktop XP syncs the folder at every logout. I do not need any sync, on the contrary: because the email files are in the documents folder I get a list of error because pst files (and a couple of other extensions) cannot be sync’d.
How can I disable the synchronisation?