Printer drivers on LAN

We have a small LAN at home. I run Windows 7, latest Service pack, motherboard is ASUS M3A78PRO. I have two devices linked USB - an HP Deskjet2480 All-in-one, and a Samsung CLP-510 laser printer. I link to a router/ADSL Modem by Ethernet.

My wife runs Vista Home Premium, SP2, links Ethernet to the router.

My son runs Windows 7 Ultimate, SP1, on a home-build, link wireless to router.

All three used to be able to print on the HP. (The Samsung is a new addition).

I have recently done a complete new installation of Windows 7 - now only I can print. My wife 'sees' the HP printer, but nothing prints for her. SOn hasn't needed to print as yet.

I have enabled 'File & Printer Sharing' - and also Printer Sharing on each printer.

I have tried to solve the problem, without success, as follows:-

Start button takes me to Control Panel.

Right click on icon for Deskjet F2400 series. There is no 'Change sharing options' button. (Network and Print sharing is already enabled.)
Click on 'Printer Properties' brings up access to 'Sharing'. Panel at foot says 'Drivers - If this printer is shared with users running different versions of Windows, you may want to install additional drivers (This is exactly what I want to do!) so that the users do not have to find the print drivers when they connect to the shared printer.'
Below this is a button 'Additional Drivers'
Click on this -brings up a dialog ; You can install additional drivers so that users on the following systems can download them automatically when they connect' and a list of 3 items under headings 'Processor Type Installed'
The types of processor are 'Itanium x64 x86' All are shown as 'Type 3 - User Mode'
Type x64 has a tick in the box next to it, and is 'Installed' The others have a blank tick-box, and are not installed.
I tried the following, with both Itanium and x86 entries - same result.
Presuming I need to install drivers by this route, I tick the box, and click OK at the foot. A new dialog appears, Install print drivers (Itanium Processor) - 'Please provide a printer driver - Type the path where the file is located, then click OK - Copy files from D:\' With a Browse button, and an OK button.
This is where I cannot proceed. I assume that the driver is on the installation disc. But, when I insert it, I can't locate anything that looks like what I need. I presume the drivers are on the disc somewhere - but where?