Quoting ulrichbrynjulfsson,
So even I have my license key for 2.0, I need to buy a new version 6 due to the fact I did not backup my old version of "fences.exe" ?
That's correct unless you bought a stand alone license for Fences 2. As an aside, I'm not at all convinced Fences 2 would work very well or at all on W10 or W11, as it worked on Windows 7 / Windows 7 x64 / Windows 8 / Windows 8 x64 / Windows Vista / Windows Vista x64 / Windows XP / Windows XP x64