Displaying only posts from one category?

I did that wikipedia thing, by editing the php, and it worked great for the main page. teh sub page, also in a sub folder, it did not work for.
Also, another problem I’m having, when you open comments on said sub page, which is http://www.nykoelle.com/blog/ (the main is http://www.nykoelle.com) The comment goes back to the index page. How can i change that?
Thanks.
Meghan

No I wouldn’t. Do you need to have the other page in an entirely different directory, too?