First make sure you have the
appropriate driver for your version of Windows 7 (32 or 64 bit).
Then determine the MachineName and IpAddress of the Desktop hosting the printer share, as well as the ShareName of the Pixma (make sure to keep it short with no spaces, just for simplicity).
Then try this;
On the Windows 7 machine (delete all reference to the Pixma that might be a result of previous installation attempts)
Open Devices and Printers
Select add printer near the top menu bar
Select add local printer
Choose Create a new port and local port from drop down arrow Click Next
In the enter a port name do one of the following
1.
\\MachineNameHostingPrinter\Printer'sShareName or
2.
\\ipaddressOfMachineHostingPrinter\Printer'sShareName
In the install printer driver dialog box do one of the following
1. In the left panel select your printer manufacturer and in the right panel select your printer model (to use Win7 native drivers) or
2. Select the have disk button and direct the install process to the folder where you have download and extracted the Win 7 drivers for your printer.