Go into Control Panel>Printers and Faxes on the PC that the printer is connected to and make sure that the printer is being shared.
You would normally see that the icon for the printer has a hand on it. (don't we all?
)
If it doesn't, right click on it and click sharing...
When you print from the laptop, ensure that the printer you select is the network printer. If you have installed the printer direct to the laptop, you will have a separate icon for it, but that one is not the one you need to use.
If you are not sure, delete any network printers already there and try to add the network printer again using the add printer wizard and selecting the second option, network printer.