CCleaner and/or Revo will make sure that these registry items have been properly removed. The reason for this, is because there will be registry items left over if you just delete the content. I personally suggest using a tool like CCleaner or Revo Uninstaller to do this, instead of simply going into Steam and clicking 'Delete Local Content'.
Lets start by totally uninstalling your current installation of Skyrim. A clean install of Skyrim, and some random OS tweaks to help performance
