Reading
netgears support site would seem to indicate the the lights are normal.
I don't think your switch has DHCP, generally they don't. I imagine your modem has DHCP capabilities, but as you have it connected now there's no link between it and the rest of the network.
I would suggest trying one of the following:
If your modem has an ethernet port use that instead of the usb, that way it can act as a DHCP server (assuming it supports this feature) and serve net access to the rest of the network.
If it doesn't support ethernet, most usb modems (actually I'm assuming it's a broadband one not dialup) will appear as a virtual ethernet adapter on your computer. You should be able to bridge this with your standard ethernet adapter under xp to create a path that your modem can communicate to the rest of the network with.
The other way is to invoke xp's built in DHCP server. You can create a dummy dialup connection and share it, doing this will allow xp to act as a DHCP server, however I don't know if this will break your internet settings and prevent your usb modem from working properly.
The final solution is download
DHCP Turbo. It's a freeware software based DHCP server and should allow you to get around the problem without buying additional hardware.