Question : Problem: Linksys router-Comcast modem

I inherited a network with a Linksys wireless router connected to a Comcast modem on a network running POS terminals that use static addressing.  
I do not have the Linksys password for the router or the secured wireless network.

I have two handheld POS computers, one works, has internet access and connects to the POS server on the LAN, the other does not, because I do not have the password to connect to the wireless network and no one knows what it is.  If I hard wire this handheld it works fine.

  The wierd thing is the Comcast modem is NOT plugged into the WAN port on the Linksys, it is plugged into a LAN port.
I tried connecting a new Linksys router (same model) and when I ran the setup wizard it did not detect the Comcast modem, but if I connect that same cable to my laptop I can get out to the internet and I get a 10.1.10.x address, so something is doing DHCP.

If I do an ipconfig from the wireless handheld that does connect it shows the gateway ip as 10.1.10.1.  When I enter that in internet explorer, it takes me to the Comcast modem not the Linksys router.
There a 4 other stations (hard wired) also show 10.1.10.1 as their gateway and they all have internet access, they are all connected to the Comcast modem directly.

Any ideas on why the Comcast modem is plugged into a LAN port and not the WAN port on the Linksys?
Someone told me that the Comcast modem is doing NAT and that the router is running software that has it in bridging mode. This saves Comcast a static IP.  I know nothing about bridging.

How can I set up the new Linksys router so it will provide wireless and wired conection for all machines on the LAN so they can all see the POS server?

Resetting the exisitng router is not an option because then I lose the other handheld if I can't getthe wireless working again.
Thanks
CJA

Answer : Problem: Linksys router-Comcast modem

Make sure nothing is in the USB port of the modem... You never know.

The site is probably a comcast business site with multiple ips. The comcast  modem will allow the first few mac addresses that it sees to aquire internet connectivity. It will not recognize mac addresses after a number set in the modem.  It may or may not continue to hand out internal ips from its own pool of IPs.
 Usually these IP addresses are a bad sign, and mean that you are not getting a comcast dhcp address, but thee cable modem CAN be configured as nated device.
You can go to 192.168.100.1 , from a working device, to see whatever cable modem configurations comcast allows you to see, including the current number of mac addresses. Comcast might have a mac FILTER set up for particular workstations.

If you plug in the new router wan port into the cable modem, and then power down the old router and the cable modem, wait 30-60 seconds and then bring up the new router and the modem after the router is fully up, you SHOULD be able to use the new router as a NAT/WAN device. You will need to reconfigure all the wireless settings.

Don't run the setup wizard for the new router, configure the router manually with a man ip address configured with dhcp.

Check to see what the current wireless channel and access point name is beforehand using windows network discovery or a program like netstumbler, because the channel is appropriately working in your environment. Check the POS workstation configurations to at least determine the wireless security TYPE, because you know it supports that at least.

How to proceed depends on your needs.  You can take a valium and a shot of good bourbon, and call comcast tech support to determine what your current configuration is and if it matches what you are paying for. You might want to have them clear any mac address filters. You may want to have more than a single IP address, you are currently paying for a few, I would guess 5.