iMac will not connect to Wifi Networks after System Update

I have an iMac which is about a 2007-08 model.  It had osx10.8 on it and I updated the software to osx10.9 the other day.  Since the update it will not connect to ANY wifi network.  We have tried multiple networks and it will not connect to any.
If I set the IP address to static it will connect but no internet access.

It detects all networks fine but just will not connect.

Help please
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Joshua GrantomConnect With a Mentor Systems AdministratorCommented:
Under Macintosh HD/ Library / Preferences /
Joshua GrantomSystems AdministratorCommented:
Macintosh HD/ Library / Preferences /

Drag the ‘SystemConfiguration’ folder to the trash or just delete it but do not empty the trash just yet. You may need to drag it back to restore your network settings to the previous.
mbellettyAuthor Commented:
Where do I find the system configuration folder
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