Enable navigation bar on CM10/10.1 on Samsung Galaxy S (1)
You can set a NavBar on your device by just adding a single line to your build.prop file.

qmenu.hw.maikeys=0  

also you can disable you current h/w buttons by 

give a # symbol before

key 172 HOME
 key 158 BACK
 key 139 MENU

in file /system/usr/keylayout/Generic.kl 

ES file Exporer will automatically make a backup for those files. You can use that .bak files if you want to revert.

you can edit build.prop file using ES file manager app

OR 

You can try flashing zip specified here