@DevilDog
Just re-download it and EXTRACT it to a folder.. The file is a .exe so it should just launch normally (just like the normal tibia client which is also a .EXE so if you can open normal tibia.exe then you can open XenoMC.exe...)
If you are using a Windows Vista - Windows 7 computer make sure you run the XenoMC.exe in administrator mode. After that when your trying to open your tibia clients make sure you open them slow just as the XenoMC Prompt says..