You can simply rename the directory name to "jv16 PowerTools 2006".
After this, you must open MainSettings.dat from the application's directory (by default at: c:\program files\jv16 PowerTools 2005). You can use any text editor to open the file, for example Notepad.
Update the directory information inside the file, i.e. change "...\jv16 PowerTools 2005\..." to "...\jv16 PowerTools 2006\..."