What is happening is Windows 7 client is looking for x64 driver on the server. It cannot load Win32 driver in x64 based system. Install x64 based driver as additional driver on your system that is sharing printer.
Here steps
1. Download x64 driver from hp.com. Possibly extract files known location
2. Open printers folder.
3. Right click on the "shared printer"
4. Click on "Properties"
5. Click on the "Sharing" tab
6. Click on the "Additional Drivers..."
7. Check the box for 'x64 Type 3 - User Mode'
8. Click OK.
9. Select directory where extracted x64 driver location to install driver
10 Click on Close
