Default printer keeps changing to printer on the network

We have a 5 computers on a network. We run Windows XP and all have our own local printers connected to our computers but we share them all on the network. Until recently, one of the computers default printer would not stay on his local printer but automatically change to a shared network printer. We did a reinstall of windows on this computer (for other reasons) and reinstalled his printer and now his default printer stays on his local printer but the other user (whose printer he kept printing to) now his default keeps changing to the printer we just did the reinstall on? IS there an easy fix for this?