how to hook up lap top and desktop?

If your cable modem can connect by ethernet, purchase a cable/dsl router.  If you want the laptop to go wireless, then the router should be a wireless router.  If the 5100 does not have a wireless network card installed, you will need to purchase a Mini PCI wireless network adapter and install it in the Mini PCI slot in the laptop.  You will then connect the modem to the WAN or Internet port on the router.  You will connect the 8100 to one of the LAN ports on the router, and the 5100 will connect to the router (and thus the cable modem) through the wireless ports.

Steve

It is always best to connect at least one computer to the wireless router by a wired ethernet connection.  It is diffucult to configure and troubleshoot the wireless network unless you can connect to the router by a wired connection.   Thus, you will probably want to connect the 8100 to the router by ethernet. You will need two regular ethernet network cables.  One to go from the modem to the router and one to go from the 8100 to the router.  You will not need a wireless network card for the 8100.

Steve

I've just set up a couple of computers like you describe.  I can't seem to get the two computers to recognize each other, even after running the network setup wizard in XP Home Edition.  I'm not sure what I'm doing wrong.

First note that when you have a new question, it is always best to start a new thread rather than replying to an existing thread.  Trying to help two different people solve two different problems in the same thread quickly becomes very confusing.  Furthermore it is very impolite to the person who started the thread.  Think of this in the future.  In the meantime, the main reasons that computers cannot see each other on networks are due to blockage by firewalls.  On any computer running Windows XP with SP1, disable the Windows XP firewall. It will not allow File and Printer Sharing. On computers running Windows XP with SP2, make sure that the Windows XP firewall has File and Printer Sharing checked off on the Exceptions tab. If you are running any third party firewalls, like those provided by such programs as Zone Alarm, Norton Internet Security, or McAfee Security Center, make sure they are configured to allow local network traffic.  If this doesn't help, or you have more specific questions, please start a new thread rather than replying to this now mixed up thread.

Steve