Trouble With Home Networking

#1
I have a Motorola Wireless Cable Modem Gateway SBG900 with Ethernet connections on the back I have no cable I have dial up. This modem is currently hooked up to my desktop which is running WIndows XP.

I have a Wireless G Plus MIMO USB Network Adaptor that is installed on my laptop that is running Windows Vista.

My laptop sees the wireless connection I just don't know how to get them to share the internet connection is this possible? Can someone please help me this is the first time that I have every tried to set up a home network as you can probably tell.

Any help would be appreciated.

Thank you.