u dont necessarily have to install things, u can find flash games and just play them, some support internet gaming.
Drag Racer Online V3 (at newgrounds.com) supports this, just DL it and play away
either that or start trying to crack the computer system, just look for back doors! thats what we did for a while at school... if u get into trouble then use the excuse that u were simply tring to make the network more secure by finding holes in its security. A good one is right-click and make a new short cut and direct it to a drive (Eg: S
and then try to access it, i found 4 drives that dont show up on the student accounts at school!