WIFI not even visible after a Software re-install?

My wife's Macbook AIR purchased in Oct 2010 has been through a lot of updates since then and was running Yosemite 10.10.2 but she lost the ability a couple days ago of wifi. The wifi icon on the upprer right corner of the screen was grey and said that there was no wifi. I went through all the help and similar posts here, tried recovery, tried to do time machine but cannot get on the internet as the Air does not have an ethernet connection.

I have just reloaded the original Snow Leopard and the Application install disks that came with the Air. Still no WIFI and it does not show in the Network under personal preferences. It only shows bluetooth.

Please help?

Joshua