If you find the font size and icons in Windows Vista hard to read than you may want to change the default font size. Many people have the misconception that a bigger screen will make everything on the screen bigger, and they soon discover that is not the case, because the screen is larger this increases the dots per inch (dpi) and that makes everything smaller. Vista has an option to make everything larger and more readable by changing the DPI setting. Lets look at how to change font size in Vista.
Right click anywhere on the desktop and select “Personalize” now select “Adjust Font Size (dpi)” on the left menu.
The UAC may appear just click “Continue” to proceed. The DPI Scaling window will pop up, select “Larger Scale (120 dpi)”
And if the default options are not enough for you than go towards the bottom you will see “Custom DPI” button. This allows you to change the font size by percentage. Play around with that option to find the perfect setting.