Hello Hot97EclipseGSX, and welcome to Seven Forums.
You're default associations for
.reg file extensions is incorrect. In
Default Programs, double check to make sure that the .reg file extension is set to have it's "Current Default" program open with
Registry Editor (C:\Windows\regedit.exe).
Afterwards, see if you are able to merge the REG file.
Hope this helps,
Shawn