Help me troubleshoot my router...PC...'net connection...?

[Felonious Monk/Fignozzle]

Okay, I am stumped and need some help.

I have high-speed cable internet access.  I bought a router that worked fine with 2 Windows 2000 machines, before we moved.
After the move, I now have 2 WinXP machines.

Either computer works great when connected directly to the modem.
When run through the router, however, one will work fine.  The other machine will give me this off/on connection, almost as if it "blinks", connects and disconnects roughly one cycle per second.

I DO recall when reformatting one of the machines, the Windows config asks whether you connect the PC directly to the 'net via high-speed, or if it is on a home network or LAN.  I've always taken the defaults, which is "connect directly to the internet".  

Does anyone know if XP must be configured differently if you are going to use a router?

Alternatively, I remember coming across an article on Tech Republic or somesuch about the need to upgrade the router's "firmware".
Since it's a CompUSA branded router and out of warranty, I can get NO assistance whatever from them.

Any 'net connectivity gurus out there that can venture a guess on this one?
My kids are bickering over the 'net connection and I've got WORK to do...and threads HERE to read!

Thanks
Fig

[Ben]

Given that I can't see your settings, one quick thing to try is
command prompt > ipconfig /all
on both machines. Read the info and make sure the machines are in the same IP range as your router (i.e., gateway). You might also try setting both machines to DHCP in network settings if you don't mind non-static IPs. You should be setting up for "home network" if you have multiple PCs hooked up to a router or router/hub combo.

Well. at least that's my opinion -- you will have others....

[Felonious Monk/Fignozzle]

Ben-- thanks.  I'll try those for starters.

After the fact, how do I go back and change it from "connect directly" to "set up for home network"?

[Ben]

Probably the easiest thing, versus using the Windoze auto setup at this point would be to goto: network places/view network connections/local area connections.

Choose Internet protocol  TCP/IP
Click on properties (write down what's there now so you can reset to it if you need to)
Choose "obtain IP address automatically"
Choose "obtain DNS server address automatically"

Do this for both computers. You don't NEED to do this, but to make sure, after I reset stuff I generally turn the router off and on as well as the computers, so that I know for sure all the setting took.

Worst case scenario if this doesn't work is to go back to what you have now so you're at least on the internet on one computer.

If you want to let windows reset your network connection, you go to network connections/create a new connection (best to delete your current local area connection first so you don't have unnecessary multiple local connections)
This will walk you through that same process you did when you first installed XP.

Keep in mind I'm just a hack -- others may (probably will) have more elegant solutions.