Can't See Shared Devices

I can't see any shared devices on my network. I have two HP/Vista computers, a 64-bit desktop and a 32-bit laptop. Did the same thing on both: went to Control Panel/Network and SHaring Center/Customize, set network to Private, checked Firewall settings (Discovery is enabled), then tried View Computers and Devices to discover computers and printers - nothing shows on either system. I have two USB printers attached to the desktop, can't see them from the laptop - I try to Add Printers from the network on the laptop, but it doesn't find any printers. Of course this is not surprising since it doesn't find the other computer.

Other things I did: Disabled the Norton firewall on the desktop. The temporary free trial that comes with HP systems disables the Windows firewall, so I enabled that. Set all Windows firewall to recommended settings and double-checked that Discovery is on. I use Avast anti-virus (the free Home edition) - don't see anything there that would inhibit network discovery. Rebooted both systems after all changes. Still dead in the water - can't see either computer from the other one. I also want to add an XP laptop to let it share printers, but haven't tried that yet.

Any ideas?