I had a similar problem.
Windows 7 64-bit with canon pixma 4500 which I wanted to share with Vista 32-bit.
Printer worked under Windows 7, connected to the Vista laptop also, but wouldn't share.
I downloaded the canon driver (NOT the add-on module) from canon for 32-bit Vista to the Windows 7 PC.
It comes as a selfextracting executable, but this will not run on Windows 7 64-bit.
Exctract it using winzip.
You'll end up with a driver folder in which you find the .inf file (in my case ip4500.inf).
It should be possible to add it as a driver for the x86 architecture through start->devices and printers, select you printer, rightclick, select printer properties and then enable the sharing options and select install additional drivers.
Click on x86 and press OK. Point to the location of the inf file and press ok.
The 32-bit printer driver should be added to your Windows 7 64-bit.
I say 'should' as in my case it did not work immediately.
Instead of installing, Windows 7 could not find the proper driver (in my case for 'Canon Inkjet ip4500 series').
To solve this, use notepad to edit the .inf file of the downloaded driver.
In it, there are 3 locations where the printer is described as 'Canon ip4500 series'.
Add the word 'Inkjet' to it at the right place and try again.
It worked for me.
Apparantly, Canon or Microsoft had been so 'wise' to rename the printer from 'Canon ip4500 series' to 'Canon Inkjet ip4500 series'. Windows 7 is so 'smart' to look for an extra driver only on your local PC (rather than find it the same way Windows update will find it) and only based on the (renamed) printer name in the Windows 7 driver (rather than the key provided by the printer itself).
Best Answer
Most HP printer files contain drivers for a family of printers, i.e. Laserjet 4, 4+, 4P. Some will contain drivers for both 32-bit and 64-bit versions of Windows.
Virtually all HP printers come with at least three drivers: PCL5e, PCL6, and Postscript. Each of these uses different command sequences to control the printer, and has slightly different capabilities. Choose the 5e for the most basic (and usually reliable) driver; PCL6 for advanced features (also sometimes necessary for increased resolution printing); Postscript for best compatibility with a range of programs that use mixed printing modes, such as Adobe products.
Which works "best" will depend on the programs you run and the model of printer. In general, PCL5e is the most reliable and PCL6 works properly with the widest range of programs.
And going against all this, HP is moving mostly to a "Universal" driver that will work for multiple printers installed.