There are a couple of different ways. First is to right click on the background and then click properties, this should bring up a selection of tasks like themes, desktop, screensaver, appearance and settings. Click on appearance and change the font size to extra large, then click apply.
Or if you click start then programs, then accessories, then accessibility, then magnifier. This will bring up a box at the top of the screen that had a magnification of whatever the arrow is pointing to, it will also bring up a settings box in which you can change the level of magnification etc. The magnifier is probably your best bet but it has to be done everytime you start the computer and if you click the exit box in the magnfication settings it will colse it aswell. HTH