Search Netgear's online support for a suitable driver. If a driver for Windows 7 (or Vista) is available download and install it. If no driver is avalable, can the adapter and buy a new one that has Windows 7 support.
I had the same issue when I first upgraded to windows 7 last year. I did some google sniffing around and found some other users who actually used a linksys driver. I tried that out, and it worked!
I've since upgraded to a wireless N adapter, so I cant go in and check my driver for you... but basically you're just going to have to put in some time working through google hits