Can't run "Hello World" in python mode

Thanks for your information and suggestions. Still not working, however. I tried:
• Renaming and moving the Processing folder from Documents onto my desktop (I wanted to keep the previous processing scripts I had written, so I didn’t delete the folder.)
• Deleting the Processing folder from my “Library”, as you suggested.
• Deleting the Processing app. (Probably to no effect.)
• Restarting computer, re-downloading Processing, re-adding Python Mode.

I’m at a loss about what else could be conflicting with Processing running in python mode on this particular machine.

Let me know if you have any other suggestions. I really appreciate the help.

-Spiff