My Mac desktop has Snow Leopard OS and my MacBook Pro (2009) has Leopard. Both were compatible with my HP Photosmart 6180 All-In-One Printer that just died. I have checked Apple's listing of printers that are supposed to be compatible with all Apple products and found various comments re inability to install or no printing after installation. I presume that is caused by lack of compatibility with certain Apple operating systems.How do I know which one to buy? (I have limited space for a printer:18" wide x 12" deep for actual machine size).