Instructions for windows XP by the way but later or earlier versions should be the same.
1. Right click on your desktop and select properties off the menu that opens.
2. The Display Properties window should open, select the settings tab at the top of the page.
3. Click the advanced button, this will open a new window.
4. If the new window has not already done so, switch to the general tab.
5. Use the drop menu to change the DPI settings to large size (120DPI)
6. Click apply, just a note you may be asked to insert your windows disc and asked to restart your pc at this point.
That’s as explanatory as I can make it, hope I’ve not been patronizing.