Hopefully you've done this yourself but just to double check.
Go to your Printers and Faxes and make sure you give your printer a Sharename on the computer your Printer IS connected.
Then on the computer that isn't connected to the printer go to your Printers and Faxes and click to add a new printer, from there make sure you pick the "A network printer....", click next and from here click on the "connect to this printer.." option and in the box below type in something like this: \\ComputerconnectedtoPrinter\Printer.
Also make sure you have printer and file sharing enabled in your software firewall.