What orchestra/symphony is this?

I don't know, it goes like...
'Dun dun dun dun, dun dun dun dun.'
3 fast A's then one F, then 3 fast G's then one E.

Yes...definitely Ludwig van Beethoven's Symphony No. 5 in C minor Op. 67 (written in 1804-08).

This clip will confirm it:
http://www.youtube.com/watch?v=zhcR1ZS2h...

The correct starting notes of the theme are G-G-G-Eb, F-F-F-D.

sounds like beethoven's 5th in the wrong key ....

That would be Hall of the Mountain King by Grieg

definately beethoven's 5th symphony

The first movement of Beethoven No 5 In C Minor