ok tell me what I'm doing wrong

I installed Mach2 Concord, followed instruction,

I go to FS2004m pick British Concord, I see the concord in small window with british livery

I press fly and windows pooping up ERROR: do u want to load this file ? gauges/........, Its might not work with FS2004, I press yes, game quites, press NO its again poping up, keep presing no and still poping up

It should be telling you which part isn't working with fs9. Find that out and then go delete that gauge.
I've had that a few times and doing that solves the problem. But...after that the aircraft (at times) isn't worth flying. That shouldn't be the case with the Concorde.
Let us know how you do.

ok now when I wonna switch view and press S, its telling me " Sound File Ugueltig"

Are you German or is your Flight Sim in German not English. "gueltig" means "valid" and if you have a download of something like Kazaa that may be causing your problem.
If you download music from the net, that could cause it also.
Let us know and we'll go from there but that's getting a little to technical for me.
Codecs and faulty Media players, ok.