Der Zähler fehlte ...
[autoit]$i = 1
Do
$var = RegEnumKey("HKCU\Software\Microsoft\Windows\Currentversion\Explorer\Mountpoints2", $i)
If StringLeft($var, 2) = "##" Then
$iDel = RegDelete("HKCU\Software\Microsoft\Windows\Currentversion\Explorer\Mountpoints2\" & $var)
EndIf
$i += 1
Until $iDel = 0