The OneCare printer sharing feature will only work with a locally attached printer, which means that any PC using OneCare and activated with the same LiveID/subscription on your local network can share an attached printer using the OneCare feature as long as those PCs are all 32 bit (XP or Vista) (or all 64 bit Vista).
You can use a network printer that is available to the PC on your local network, but not through the OneCare feature. You will need to configure/install in manually per the manufacturer's instructions. If the printer requires special software, it may need to be allowed in the firewall. If it requires ports to be opened that are normally closed, these also need to be added to the firewall configuration.