Add punctuation: 13 He led them through the abyss like a horse which does not stumble in the desert
A: 13 He led them through the abyss, like a horse which does not stumble, in the desert.

Add punctuation: In order to install Windows Undelete it is mandatory for you to be a member of the local administrator group or possess an equivalent level of rights and UAC must be disabled
A: In order to install Windows Undelete, it is mandatory for you to be a member of the local administrator group or possess an equivalent level of rights and UAC must be disabled.

Add punctuation: Families who have purchased 1 van and leased 1 private car
A:
Families, who have purchased 1 van and leased 1 private car