I just installed Windows 7 and got my WG121 Netgear USB adapter working. I downloaded the drivers
from Netgear. Here's what I did.
Went to WG121 Software V2.0
on NetGear's support site.
Downloaded the wg121v200.zip
Created a System restore point (just to be safe)
Unzipped and ran the setup program.
Ignored all the warnings and finished the install.
After the install was done, I plugged in the adapter and it took a little while but it recognized it eventually.
Then followed the Windows 7 wireless setup process to connect to my router.
Hope that helps.