GAMER LOUNGE 20XX (NO CASUALS!!)

[Kosheh]

Does anybody know if it's possible to associate only a specific file with a program as opposed to every file with the same extension? (Windows 8)

No. It isn't.

What a Supple, Informative Post

But yeah, what Goemar said lol. You're pretty much just stuck with right-click > "Open With".  Once you search and find the program you'd open it with, it usually shows up under the "Open With..." menu whenever you right click on a file with that extension.

...You could also just drag the file into the app while it's open, but your mileage may vary with that option