I'm used to pressing alt and using middle-click drag-n-drop to resize windows in gnome, and pressing alt and using left-click drag-n-drop to move the windows around. or again... pressing middle click on a scrollbar to make it jump to that position.

KDE has a similar behavior too.

...but when I use someone else's PC, or a Windows terminal somewhere, it doesn't work...

I use linux pretty much exclusively at home. arg.

Is there like a portable app that I can shove on my USB stick, that when executed, it changes the behavior so the above works?

That drives me nuts too. The middle-click-copy behavior is something I am always missing when outside my familiar environment.

I suppose there isn't any program that just tweaks windows to look and feel like linux?

Personally, I just don't use Windows.

But there certainly could be such a program. I'm not a person who would know... it's been years now since I've actually used Windows for anything but... well, anything.

I prefer to use linux too... however, not every computer I come accross runs linux

I'll have to take a look around google.