Can't Drag Files From Explorer Into 64-bit Programs

I've been having this issue and trying to wrap my head around it for a couple weeks, and I've had this new laptop less than a month. Just as I was posting this, I realized that it seems to be specifically 64-bit programs.

Specifically, the problem is that when I try to drag a file from Explorer into a program that I know is able to load it from drag-and-drop, all I get is the "no" pointer, the circle with the line. All the programs I've tested would let you drag files onto them just fine on my older Windows 7 laptop.

Some of the specific programs this is happening in:
Microsoft Office 2010 (seemingly the whole suite is acting like this, I tested Word and Powerpoint)
Paint.NET 3.5.10
Sony Vegas 12.0
Waterfox 18.0.1

I can File>Open files in these programs just fine, but dragging to them from Explorer would be miles more convenient. I've tested the files I've tried dragging. They drag fine into Notepad, they drag fine into Foobar2000, IrfanView, Notepad++, all operating as 32-bit.

Now I WAS having the same problem with Audacity and Skype, which is why I didn't catch the pattern of them all being x64 programs at first (since I have 32-bit versions of both), but that was happening because they were being run as Administrator, which is an issue I'd also like to try and resolve. I don't understand why running as Admin should prevent me from dragging files into open windows of them.