if you have it attach to the vista machine share it out..
Go to Control Panel\Network and Internet\Network and Sharing Center\Advanced sharing settings:
Turn on network discovery, (Do all this for both machines)
Turn on file sharing and printer sharing (Do all this for both machines)
I turned off public folders its up to you (Do all this for both machines)
Also go to Control Panel\Hardware and Sound\Devices and Printers find your printer right click and click printer properties go to sharing click share this printer then name the printer w.e you want
After that's all done on vista machine go to win7 machine type in address bar the vista machine name so for ex if you open my computer were it says my computer type ---> \\vista-PC then hit enter
(if you don't know your PC name right click on my computer and go to properties > look for computer name, domain and workgroup settings > if you click change settings you can change your computer name requires a reboot)
You should see the printer that you are sharing
Right click can press connect.
You know if your printer has networking capability you can just plug it into your router and set an IP