Hello and Welcome to TSF,
1. Unplug your USB cable from the back of the Windows XP PC and plug in the usb cable to the vista pc.
2. The Windows Vista drivers for your printer should be automatically loaded and your printer will be installed on your Windows Vista PC. If this was successful, skip right to step 3. otherwise,
Download driver and software here:
http://welcome.solutions.brother.com...=English&dlid=
If you had to download the driver and software,
then unplug usb cable form the vista pc.
1. install the driver and software, Choose the option to proceed with installation without connecting the printer.
2. reboot pc
3. open the Printers icon in the Windows Vista Control Panel.
4. right click and choose properties properties (on printers icon)
5. go to ports tab
6. Click Add Port, then select Local Port, then click New Port.
7. For the Port Name, enter the exact network path and share name of your printer.
8. Click OK and make sure that this new port is selected with a check in the checkbox.
9. Click Apply and then OK to close the printer properties.
10. turn off pc, connect the usb cable to printer from the vista pc, turn on pc.
11. You should now be able to print from your Windows Vista PC to a shared printer located on your Windows XP PC.