If you have a 2Wire 802.11g USB adapter, legacy or current, you can use it on Windows 7.
First you need to identify whether you have a legacy or current adapter, and then you need to find out if you have Windows 7 32-bit or 64-bit. The great people at 2Wire have put together a support page that not only shows you how to do both of these things, but also provides you with screen shots showing you how to complete driver installation on your Windows 7 system.