vTask is compatible with 32 or 64 bit environments (or so they say), so the script should call the 64 bit version of Regedit when needed. Anyway, after many hours of trying different combinations, I was able to deduce that the only key that cannot be modified when it is being called from vTask (or AutoIt, or Autohotkey for that matter) is "HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Run". The "Wow6432Node" variants of that same key can be modified with no problem. Finally, I remembered that Registry Workshop had command line support, so I replaced "Regedit.exe" for "RegWorkshopX64.exe" (wich installs on Program Files, not Program Files x86) on my script and it worked perfectly, I was finally able to modify "HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Run" again. I hope someone else find this info useful in some way. AutoIt or Autohotkey suffer the same limitation of vTask in this case. Thank you.