Office 2003, of which Publisher 2003 is a component, is compatible with Windows 7. Although if you ARE going to be spending money, you'd be better off getting the 2010 version which offers (if you'll forgive the highly compressed description) better performance, stability and features...
My Computer
At a glance
Windows 7 Professional 32-bit SP1AMD A4/A63.00GB EDOVMware SVGA 3D