Why wont ATC talk to me ??

[rafvr27]

Decided to have another crack at Vista - installed it in new hard drive then installed both FSX and FS9. They both fly OK but
whilst in FS9 I get full sound around the aircraft and in the cockpit and ATC functions correctly - when I try FSX the sound
is not good. I get no engine sound in the cockpit and outside it is in stereo - sound left or right as I move around the
aircraft. However in ATC I get the selection of commands in the window but no atc voice.
I`ve checked and double checked the configbut am stumped. Why FS9 but not FSX

Any clues, guys

Regards

George