The easiest way is to change the DPI from 96 to 120 in the display settings. You can also go through and increase the font size for different Windows GUI controls, and I think there are even a few "large print" options pre-configured.

Dropping the resolution is probably the easiest thing to do though. If your friend has an LCD monitor, it will have 3-4 native resolutions, so you can just drop back to the one before the highest resolution. My 20" has a max resolution of 1600x1200, and the next step down would be something like 1280x1024, then 1024x768, 800x600, 640x480, etc. Anything with the 4:3 aspect ratio. If you have a widescreen monitor, the aspect ratio is a bit different, but the same basic concept applies. Maintain that aspect ratio, and the image quality will not be degraded at lower resolutions.