3d surround (1 Viewer)

hello everyone,
m using a 5.1ch home theater system and have connected it to pc. i love watching HD movies with 3d surround sound but the problem is whenever a person speaks in the movie i cant hear what he's telling but when someone speaks on the right or left side of the screen in movie crystal clear voice can be heard from front&rear speakers but sadly not the same with center speaker. so only i select some other options available in the video player( ex: reverse stereo, mono, stero & 2front 2 rear). i used to connect it to DVD player and everything was just fine but now i have connected it to pc and doomed myself. ...
please suggest what to do?...wat is actually going on? ..
my system: http://www.fendaindia.com/products_view.asp?id=45
please help...
regards,

see if u r actually outputting 5.1 ch to ur receiver/amplifier. That is the problem at times with PCs, u have to tell it to output the proper format.
If that is fine, see if u can just increase the volume level on the center channel.
Also, run some kind of 5.1 channel test from the PC to check that everything works as it should.
Let us know what happened, OK?

i got it...its working now...there is an option in my system called "pro" which should be turned on only when playing non surrounding files lik mp3 etc...but while playing true HD movies n all which are deemed to be made up for 5.1 surround "pro" must be turned off in order to get the surrounding effect...i sorted it out yesterday and now everything's working just fine but again there is a problem which is as you said i have to tell the pc to output in a proper way everytim i turn on the pc coz it CONFUSES A LOT with the speakers....is it a problem with pc or home theater? m just asking though i haven't tried to connect it with other 5.1 systems til now. pls suggest how make it a default configuration?
thanks