Segoe UI is default on Vista.
I've looked at the code and the only change I made to the function that determins which font should be used as the default one by all the forum is pretty much the same as it's been for over a year.
I say 'pretty much' because it's is slightly different now if you're running an OS dating back to before v5.0 (v5.0 = Windows 2000 so anything before it would be Win 9x, Me and NT)
On XP and Vista there's no difference.
When the program picks which font to use, it calls with SystemParametersInfo ( http://msdn.microsoft.com/en-us/library/ms724947.aspx ) with 'uiAction' set to 'NONCLIENTMETRICS' ( http://msdn.microsoft.com/en-us/library/ms724506(VS.85).aspx ).
Assuming that call succeeds, it then uses the font names from (and in this order):
lfMessageFont
lfStatusFont
lfMenuFont
'lfMessageFont' is supposed to be the one used by message boxes etc.
If you want more info on what's happening, open HKCU\Software\ImgBurn in RegEdit, find 'GENERAL_ProgramDebugMode' and change it to 1.
Now run the program, look in the log window and copy+paste everything you see.
You should notice that it tells you which font was selected etc and it'll give us a clue about which function / value is actually being used to set it.