If you set the dots per inch (DPI) higher than 96, and you're running the Aero desktop experience, the text and other items on the screen might appear blurry in some programs that aren't designed for high–DPI display. To avoid this problem, follow these steps:
To make text and on-screen items clearer in programs that aren't designed for high DPI
Open Display on Control Panel
In the left pane, click Set custom text size (DPI). If you are prompted for an administrator password or confirmation, type the password or provide confirmation.
In the Custom DPI Setting dialog box, select the Use Windows XP style DPI scaling check box, and then click OK.