Hm... But that's 2,754,895 KB...

So, whenever I try to re-install GMS, I get a warning:
"The folder contains a program that is running.
Would you like to continue installing after quitting the program and deleting the folder?

Folder : C:\Nexon\MapleStory
Program : MSSetupv104.exe"

Yes. It wants me to move itself, the previously mentioned 2.7 MB file. Turns out, that alone would take a couple hours. I made the folder "C:\Nexon\MapleStory" the other day when I was trying to find somewhere to put the installer.

So, any way to fix this besides moving said 2.7 MB file or redownloading?

I stand corrected.
3rd time's a charm.

you could have changed the folder name?

why were you trying to install something to the same directory the installer was located in to begin with?
the nexon installers all delete the content of the directory you're trying to install into.

and its not 2.7mb, it's 2.7gb
its basically trying to move the installer itself to another directory while said installer is running.