You Can block websites without any software.

Just follow the following stepsSteps

1] Browse C:\WINDOWS\system32\drivers\etc
2] Find the file named "HOSTS"
3] Open it in notepad
4] Under "127.0.0.1 localhost" Add 127.0.0.2 www.orkut.com , and that site will no longer be accessable.
5] Done!
example :
127.0.0.1 localhost
127.0.0.2 www.orkut.com
www.orkut.com is now unaccessable
For every site after that you want to add, just add "1" to the last number in the internal ip (127.0.0.2) and then the addy like before.
ie:
127.0.0.3 www.gmail.com
127.0.0.4 www.rediff.com
127.0.0.5 www.google.com