Hi,
In general I don't recommend to do this, because you will lost the mobile layout, but if you really need you can do the following steps:
1) Remove the tablet.css and mobile.css files declarations in the framework/helpers/helpers.layout.php file
2) Set in the template.css file min-width for the body element to a proper width for your website (with added paddings, so if you want to show page which is 1000px and have paddings please set min-width for body to 1020px).