Can't install Flash Player, followed all instructions

I can't install Flash Player on a Windows 7 machine using IE11.

I get a "failed to register" error, and despite following all instructions to the letter, still get the same error.

Uninstalled Flash, Installed SubInACL, Ran: reset_fp.bat, restart, install Flash

This has been a problem because I can't upgrade AOL, or set up my HP printer without Flash installed.