You can learn a fair bit at

http://www.programmingtutorials.com/

The top statement is mostly true, Commercial apps though are written in all sorts of languages, I've seen most written in VC++ (MFC) but lots of others in BCB, Delphi and VB. Some get written in RapidQ (basic) and it's difficult to tell because they compile to stand alone exes and the interface is quick (math is a shocker though).

but in the end, if it's prefessional and does what it's suppoesed to well then who cares? the customer is not going to pull it apart and say

"OI OI! This isn't C!!"

Get a descent (free) install program like INNO and you can distribute a 1.5mb setup exe with the full app.
(I don't like the setup system that comes with VB6)