Windows 7 to Vista network printing - yet again

I first posted this, wrongly I think, at the end of an old thread and have had no response yet. I know this issue has been done to death many times but hope someone can help me in this case, which I think has a difference.
I have a wireless home network with a Vista 32 bit at the centre with a Canon S900 printer attached, and until recently it worked fine with laptops running Windows XP, but I have just got a Windows 7 (64 bit) laptop and, although I have got all other network communications going (by the end of day 1), at the end of day 7 I can still not get the Windows 7 laptop to print via the Vista PC.
I think I can assume I have all the firewall/router connections sorted, because file sharing works fine in all directions, and if I connect the printer directly to the Windows 7 laptop by USB I can print back to it from the Vista machine. With the printer connected to the desktop, however:
1. If I try to Install the network printer it says “No driver found”, and wherever I try to direct it to find the driver (including on its own C drive, where it has the driver that works in Local mode) it only says “Windows cannot connect to the printer – Operation failed with error 0x00000214”.
2. If I try to connect as suggested by creating a new local port, and addressing the printer by \\VISTAMACHINE\SHAREDPRINTER, it just says “Access is denied”, although there are no corresponding log messages in any of my firewalls.

I think the problem must be with the driver, because the Canon 64 bit driver is only available as an add-on, rather than as a separate driver. I can download it as an executable Zip file and run it on my Vista machine, and it appears to install, but when I look in the Printer Properties, it does not have the box ticked for x64 in the Additional Drivers section. If I try to install it there manually it doesn’t succeed because it looks for a .INF file, and wherever I point it, it says “The specified location does not contain the driver Canon S900 for the requested processor architecture”.
Does anyone have any suggestions, please?!!!!

I must admit I would rather not have to get an extra piece of equipment and quite like solving problems like this - or getting someone else to solve them for me! I guess it would solve the problem if I upgraded my desktop PC to Windows 7, but again I would rather not give the money to Mr Gates if I can avoid it!
Is there no-one out there who can give some advice on this driver issue?

Thanks to those who tried to help, but in the end the answer was more basic. I had set up matching user accounts on the Laptop & server, but I had not entered a password, I read on a 'File-sharing' forum that you must also have the user accounts with passwords because Windows doesn't think unprotected accounts are safe enough! This is worth emphasising because I am still seeing requests for help with file sharing on mixed (32 bit & 64 bit) networked machines.
My machines and printer are communicating fine now.