I'd really appreciate it.  Treat me like an idiot and tell me how to 

take everything off my hard drive, 

You can run both versions side-by-side

 

Or - follow Poppet's advice

 

http://www.avsim.com/topic/475951-uninstalling-prepar3d/#entry3306633

http://www.prepar3d.com/Prepar3D_Download_and_Install_Instructions_v2.pdf

 

although perhaps you should fix the double-posting problem first !