I will explain you an easy way to set WordPress on a subdirectory, even if you have WordPress installed on your root folder. A lot of people and sites want to display a front page as their main site and not their articles or posts. A good example of this, is Matt Cutts. You can see his blog at www.mattcutts.com/blog. Instead of installing his blog at mattcutts.com he decided to put it on mattcutts.com/blog. The easiest way to do this is by creating two pages in WordPress.
First you create a blank page called “Blog” or whatever name you would like to use. (Dashboard -> Pages -> Add New). Then you create another page that will be your front page. I called it Parent Page for this example. Save the changes and you’re done. That is it. You will see a front page in “yourdomain.com” and your blog articles on “yourdomain.com/blog”. You can then customize your front page to fit your needs. For example, the sidebar can be removed to make it a full width page, insert tables, etc.