There are a number of different ways you could do this. Depending on your skin and site setup, you might have a few different options, and without knowing more about the site in question it would be hard to tell you what the best option is.

One way that will almost always work is to use a page body class (you can set it under page settings, the input labeled "Custom Body CSS Class"), and then hide your menu with CSS.

.my-pagebody-class .vertical-menu { display: none; }

Replace "my-pagebody-class" with whatever you put in that input in page settings, and then "vertical-menu" with whatever the CSS class of your menu is.

This may not be ideal though, if the menu is in the left panel of your site it will still cause the left pane to render, which will very likely mean your center content will still be pushed over, which will look odd if you don't have any other content in the left pane on that page. In this case, you can use the same body class to hide the left pane by using the CSS above and replacing the "vertical-menu" bit with the class of your left pane. You might also want to increase the width of your center/right panes.

I may be able to tell you other ways if you tell me more about the site, or give me a link.

Hope this helps,
-Isaac