Well as I already mentioned you can hack any system as it is conected to what we call INTERNET. To connect internet a system allocates a port for communication and Data Transfer. So we got to do is to get into that port that is to be hacked.
Steps: -

1. Software PORT SCANNER from google
2. The IP address of the victim whose port is open
3. NETLAB which gives u all information includes victim IP address,Area from where he is accessing internet
4. The IP of victim u found initially into NETLAB .
5. Thats it now you can access his system.

Note : This is really Hardcore Hacking and you should be very much careful while doing all this and you do all this on your own responsibility. This site is never responsible for anything you after reading any article from this site and there are almost 50-50 chances that you may get caught so don,t try this unless you are aware of everthing. Yes you can freak some of your friends by telling them that you can hack their systems very easily.