MacBook Air Wifi Icon Greyed Out With Cross Solution

I was messing around with my Macbook Air trying to get a Usb TP-link Wifi adapter with no OSX driver support  to work I am not quite sure what I messed up but on restart my I had lost wifi connectivity and a greyed out tool bar Icon with a cross appeared ...

I knew it was not a hardware issue because it did work when I logged into the Guest account. I tried many things to fix it but in the end the only solution that worked was to reinstall the OSX by pressing cmd + p + r at startup until I got a menu with that option.

You will not lose your files and you will probably gain space on the HD.