New Router, Now Two Networks?

[J-Mac]

I decided to replace my older Linksys BEFW11S4 ver3 router with a newer Linksys WRT54G v5 router. I have a home wireless network consisting of two PCs: One desktop HP Pavilion and one Dell Inspiron 8600, both running XP Pro SP2 with all Windows Updates current. The HP runs Trend Micro's Internet Security 2005, while the Dell runs Zone Alarm Free and AVG Free. Firewall permissions are OK and there does not appear to be any issues there.

The network that was in place with the BEFW11S4 was named HOME, and I had the above two plus two other PCs all sharing in the network at that time.

Now, however, the HP desktop PC is a member of HOME, while the Dell notebook is a member of WORKGROUP. Both access the internet via the cable modem through the WRT54G, but I cannot access either PC from the other as they are in separate networks.

I didn't knowingly setup the WORKGROUP network; did the new router's network setup create it for me? I used the manual setup process, but it was still quite a bit more automated than the BEFW11S4 was three or four years ago. How can I reduce HOME and WORKGROUP to one, happy home wireless network and have sharing access between my two PCs again?

I am the only user of both PCs, so internal security is not as much as an issue as it is with some folks.

Thanks in advance for any and all advice.

[Phoenix]

On the PC that got changed do this (from Microsoft website):

The Windows XP Network Setup Wizard
The Network Setup Wizard automates some of the tasks involved in setting up a home network. It's especially effective with Ethernet® networks, saving you the trouble of configuring some of the other computers on the network. You'll have to make sure all your hardware is connected properly and ready to go, but much of the behind-the-scenes work is handled for you. The Network Setup Wizard has been improved for Windows XP Service Pack 2 (SP2). Launch it by opening Control Panel and clicking the icon.

When it asks for the network name type in "HOME".