Network printer

Wow, after reading the posts here I am amazed I got my vista/xp
network going without too much problem... not because I know what I'm
doing; just lucky I guess.
But I do have one problem that stumps me:
My network is 2 desktops with XP home SP2 wired to a router. Then a
notebook with Vista Home Premium wirelessly connected. I can access
all my shared files from any of the three computers so that works
fine.
I have a printer connected to each desktop. Each desktop can use
either printer.
I want to access the printers from my notebook. The one installed no
problem (Canon i550) and works fine. When I try to install the other
(HP PSC 1500) I get a "cannot connect; access is denied" message....

Why does one work flawlessly and not the other?

Both PCs use only Windows Firewall.......

Probably a simple fix but I can't find it so any help greatly
appreciated.

Bevin B.