Doing this will lose all the drivers for the laptop's networking, modem, sound, video, and potentially important motherboard drivers.
And it will end up making your sister spend about half of one of her vacation days trying to figure out which frigging laptop model you own, downloading drivers, burning them to CD, and installing them back on your laptop so it will work again.
This will make your sister testy even if you attempt to placate her by bringing her a quad-shot caramel Frappucino from Starbucks.
And when your sister fixes it and tells you to get all the Windows updates as SOON as you plug it in at home, DO IT.
If you do not, then you really haven't SEEN testy.
And your sister can probably garrote you with an ethernet cable.
You have been warned.