I moved your post to the Firewall topic, since the problem is not with the Printer Sharing functionality in OneCare, but rather Windows Printer Sharing.
I assume that the problem occurs on the 64 bit laptop which is set to use the printer that is attached to the desktop PC. Is OneCare installed on both PCs? Open OneCare and click on Change Settings. On the Firewall tab, click on "Configure Firewall." Is the network shown as "home or work" on both PCs? If not, click Change location to make it so.
Click on Advanced Settings on the Configure Firewall window.
On the Ports and Protocols tab, place a check mark next to both entries for File and Printer Sharing at the top of the list.
On the Network Connections tab, are there multiple active connections shown?
Note that you would not be able to use the Printer Sharing feature of OneCare in your environment as you have a 32 bit host and a 64 bit machine, so drivers would not be available for this feature to work. Manually sharing should, however, work fine.
When you find that no printers are found, are you able to "find" the printer manually on the laptop and use it?
-steve
