Maybe you could temporarily make a new admin account but
first I'd consider a bigger hurdle....
Your friend's laptop.....I'm guessing it's not an Android laptop (if there even is such things)?
I don't think there's a DX9 install for Android but I could be wrong.
I haven't found a way to play Unity Web Player games
on a tablet or phone. Sorry.
Maybe someone else can help you out.
Or maybe you can install Windows....but then that might get you in trouble
with your sister or parents.
I dunno, sorry.
But fortunately there are other ways to entertain yourself
with a tablet.
If your tablet has no USB ports,
you can buy a short cable (costs something like £1 = approximately €1.36)
give or take, which connects from the tablet to a USB port that you can connect USB
devices such as USB sticks, Xbox 360 controllers, PS1,PS2,PS3 controllers
and possibly some other types of controllers.
You can even connect a keyboard and mouse.
I think a lot of apps don't work with controllers but
some do, like Playstation 1 emulators (EPSXE for example)
and possibly some Android games, dunno.
I think it might be possible to use your controller as a remote
when watching videos, but not sure.
You can watch videos, read digital comics (maybe in PDF form?)
or books, etc.
If your tablet has an HDMI port, you can connect it to your TV
and watch videos like that. If you don't have an HDMI port,
I'm not really sure how you can get it to work.
Hope that helps you in some way.