Hi,
As the printer is quite old the CD is not intended for OS X version 10.6.
First uninstall any incompatible software and then install the software below to allow printing:
Scanning is no longer supported since OS X 10.5 as you may find listed below:
You may try 3rd party solutions as Veuscan which supported your all-in-one device and compatible with Snow Leopard.
http://www.hamrick.com/vuescan/hp_officejet_4200.html
Regards,
Shlomi