Just because someone works for an IT company does not mean that they are necessarily able to maintain a windows laptop, you are assuming that the person, even if they are in a technical role, actually works with Wintel based equipment which is not necessarily the case. In fact a lot of places will just reimage to a standard build instead of lengthy investigation on software issues so that the member of staff can get working again. What Wesyfield2 says is used in the corporate world, (I have local admin rights on my corporate laptop and if I want to install anytihng on it I have to be able to proove that it is licensed for business use even if it's freeware), but it would be madness to do this in an academic environment due to the trouble their "user" could then cause, in fact my best mate is a manager at an universities IT department and is always complaining about the problems he has over this sort of thing.
What is on other laptops and what has been configured on them does not matter ... you have installed unlicensed software, i.e. Windows 7, and the current owners of the device, i.e. the School or LEA, could be liable due to that license breach. The is something the ICT department is liable to take very seriously.
You keep on saying that you'll take the responsibility but that responsibility is not yours to take. He is the "keeper" of the laptop and the buck will stop with him. You have just enabled him to breach the agreement which was probably made for the acceptable and continuing use of the device when he received it.
The laptop has been provided as a learning tool ... that learning does not include screwing around with it in this way. For that sort of thing use your own equipment.