5.1 motherboar acting as 2.1

I have recently completely shifted from windows to ubuntu linux gusty gibbon 7.10.

My Problem is that my 5.1 sound supported motherboard is acting as 2.1. Though i get sound from my woofer(Centre probably) and 2 speakes but there is no sound from other 3 (2 rear + 1).

I searched a lot but failed to find solution ... also there is no option of surround in my alsamixer to select only PCM.

I was successfully using my 5.1 speakers in windows VISTA using realteck audio driver which came in the CD, so my hardware is all right,

Also all jacks are properly plug in and changing thier position changes the speakers from which sound comes but only 2 of them workat a time (they become front) and another become soundless.

I am providing with screen shots ... please help me out.Thanks

Here are the screen shots ->

1. My Hardware information
http://www.esnips.com/doc/83b6be18-5...9d1/Screenshot

2. My Alsa Mixer graphical window
http://www.esnips.com/doc/99183840-c...7/Screenshot-1

3. My AlsaMixer Edit -> Preference Windows (No Surrond Option)
http://www.esnips.com/doc/1e85b686-8...7/Screenshot-2

4. My Alsa Mixer terminal window
http://www.esnips.com/doc/0897b4cf-b...2/Screenshot-3

If any other screen shot is need i will gladly provide it.I hope i have adequate information.