depends on what you mean, I guess. Windows hid the font change interface so its really annoying and difficult to change it now or see what it is. I think its in the registry, though? Or it may be blank until you over-ride it.
However, your program should automatically use the current system font, if it has been changed, so there is likely some squirrely switcheroo going on somewhere to load the current one and apply it into your program (and more than one, one for menu, one for title bars, one for text boxes, and on and on they go-- its not all one font, or it used to be different way back, I cant see well enough to say anymore. ).
worse, I think their new 'themes' thing can change the default? I dunno, I don't use it.