I'm trying to set up a wireless network for my neighbors; However, it just ain't working.

The modem has ethernet and USB capabilities, but thanks to a lightning strike, the ethernet port is shot. It also fried their network card, but they replaced it last night.

Here's what I've got:

Netgear WGR614 ethernet router
Motorla SB5120 Cable modem (shot ethernet port)
D-Link DFE-530TX+ PCI Fast Ethernet Adapter (rev.F)
Windoze XP, Home edition

The cable modem gets an internet connection with the usb connection, but not the ethernet. Brand new network card, so it shouldn't be that.

Is there any way I can work this so they don't have to by a brand new cable modem?

If there is a desktop PC on the network, you can set up the modem via the USB connection and then share that PC's Internet connection onto the wireless network to be used by other wireless-connected desktops and laptops. However, if the only device on the network is a wireless laptop, then no - you can't get around buying a new cable modem if you want the Internet connection to be available around the house wirelessly.

The modem is connected to a desktop PC; they just bought a laptop which they'd like to share the connection with wirelessly.

It's been a long time since I set up a network... how would I share the connection with the router?

You'll need to use an ethernet cable (or wireless connection) to link the desktop to the router and then enable the wireless network on the router and connect the laptop to it wirelessly. Then run XP's Network Setup Wizard in order to get both the PC and the laptop using the the PC's Internet connection.

This is going to be more confusing to set up than a normal network. The router won't actually be acting as a "router" at all - the desktop PC will actually be the router, routing Internet traffic out of the LAN and down the cable modem connection. The Netgear device will simply be a "Wireless Access Point" - giving a point for the laptop to connect wirelessly onto the network.

If someone wanted to pay me to do this, I wouldn't. I would make them replace the cable modem so that I could set it up the normal way. I've found the Network Setup Wizard to be troublesome in the past. It would probably be cheaper to buy a new cable modem as I would then expect to get it up and running that much more quickly. Good luck if you're going to do it the hard way!