Some dictionaries seem to indicate that 'TO' in some sentences is just there to 'mark the infinitive', thus giving meaning to the sentence
and they list examples like these:
I want TO open the window
I want her TO open the door
but that can't be it... the same definition of 'TO' for all sentences. Especially since I see two people involved in the second sentence, and that seems to be enough to call them 'different'. Two people, two actions, how are they really affected by that 'TO'? What role do they exactly play in the sentence, grammatically speaking?
In sentences such as the following:
I want her TO open the window
I need him TO give me money
I asked them TO leave the room
I ordered them TO shut up
Are the objects(people) to be the doers of the second action(infinitives)
she will open the window
he will give me money
they will leave the room
they will shut up
and that that is what I want/need/asked/ordered?