Gentlemen, it was the variable indeed, but I think there might have been some change in the Run menu from 2.5 to 2.7. That might not be the case though. I did state that I don't know much.
This turned out to be a great exercise in resourcefulness. I went into 3 IRC chat rooms, emailed 2 groups, queried 3 friends, posted in a forum, did a system restore and became more familiar with a registry. Maybe you can appreciate that. Maybe, also, you can appreciate my embarrassment after discovering that I was making a beginner's mistake, and that I had wasted everyone's time as a result...and, perhaps, you will note that I took the time to mark this as "resolved" and confess my ignorance. I was tired after 13 hours and agitated and in an incommunicable state. Perhaps you'll forgive. I did thank you guys, I think. Thanks again for the attempts.