Is there a way (without something drastic and system-wide, like turning off UAC) that I can get Windows to stop nagging me about launching MM7? I tried installing to a non-program-files directory but it didn't help.

There is some external software that can do it, but I haven't tried them myself. Just google for "disable UAC for one program" and you'll find a few.

e.g.:
https://www.raymond.cc/blog/task-scheduler-bypass-uac-prompt/

Thanks. This tip worked for me: http://lifehacker.com/how-to-eliminate-uac-prompts-for-specific-applications-493128966

Essentially, you use task scheduler to avoid getting the UAC dialog.

I know on Windows 7 this is caused by a little-known "feature" called Installer Detection. It scans programs and their descriptions for certain key terms, if it "detects" an installer it will refuse to run with no admin privileges.

It's a completely idiotic disservice to the end-user, forcing them to give admin privileges when they aren't needed and exposing their computers to unneeded risks.

I'm not certain if Windows 8.1 does this, but I would guess that it's in 8.1. Anyway, for help on disabling it, just type "windows 7 disable installer detection" into Google. The instructions might be slightly different on Windows 8.1 though.