I can launch Prism, but not start a new project or open an existing Prism file. I get a message citing a fault in module "windows\system\GDI.EXE".

GDI means Graphics Device Interface. This is the part of Windows that controls your display. To fix the problem, try the following:

1. Reduce the video acceleration: Click "Start.. Settings.. Control panel.. System.. Performance.. Graphics". Change the acceleration to a lower setting.
2. Adjust various settings in the Display Control Panel.
3. Update the video driver software, available from the computer manufacturer or the display card manufacturer.

Most likely the first approach will solve the problem, and the lower acceleration will not noticeably affect the operation of your computer.