I used to have this problem too...
But I managed to win the battle!
You definitely need to "make yourself busy" and do stuffs that do not require you to use the computers or access the Internet. I guess you are not working right now as you have 10 hours of free time to surf the net?
You might wish to meet up some friends and have a gathering, visit a library or even go shopping! Just do something away from the computer! When you are away, sometimes you still have the urge to go back to your PC. I called it the "withdrawal symptom". Its ok and normal to have it. Just force yourself to do other stuffs and gradually you will feel alright not to have the PC. It may take just a few days or even weeks. It really depends on your determination. But it should not take you too long since you know its an addiction and I assume you want to get rid of it asap.
If you really can't get away from the PC, like you are studying or doing a school project, and you need to use MS Office or Internet etc. The best way is to set a limit. Maybe you can do your "real stuffs" for 1 hour, and give yourself just 10 mins for a break and to surf net. In other words, 10 mins of net surfing for every hour of work done. Its still productive in this way!
You can quit the addition! In fact, if you don't reply this thread for more than 10 days, it means you have successfully cure your net addiction.