The installer drivers
are in system32/driverstore/file repository.
Your previously installed drivers are in system32/drivers. So if you can access your old installation you can browse the driver
(s) which had previously worked for your NIC in there. You can even copy the entire folder to later browse for any needed drivers.
Most all drivers are provided by the Windows 7 installer or follow-up Updates. But since you may need your NIC to do Updates, you are right to try to save it in advance. If it isn't in the driver file, go to the manufacturer's website and download it from there.