Windows 7 - 5.1 sound (AC3) in windows 7

Hey guys
I wanted to ask about the sound in 5.1 mode
To date I have used windows xp and all kinds of viewing software such as VLC and BS and of course K LITE-coded and everything worked fine and very high quality

Yesterday installing windows 7 ultimate 32 bit and now I can not hear sound 5.1
I tried everything I installed my sound card to a modified version windows 7
And he works very well. And installed coded all types and still do not get 5.1 sound
Now what is strange is that when I went to the AC3 filter I see 5.1 indicator but it does not come out on into my receiver via optical port
Are you recognized the problem and what should I do?

Modified Windows 7?

I'm sorry I did not understand the question
I installed windows 7 ultimate 32 bit
And I installed all the drivers for my computer
Sound card video card driver and all other
And installed as usual BS PLAYER
And K LITE
No sound comes out 5.1

this is what I meant.

Yes I installed my sound card software that fits windows 7
My sound card is relatively old and its software suitable for older operating systems and not for windows 7
So I downloaded from the site of the sound card and appropriate software to the latest windows 7 and I installed it and still does not work for me
I see in the AC3 encoded indicator for indicator 5.1 is working
But do not get through the optical port on into the receiver

If your optical out put is on your motherboard it is probably disabled since you installed a sound card. Can you get sound output from the mini pin sound jacks?
Manaually run a check for Windows updates to see if it will install a missing driver.

Forgiveness may not have explained myself correctly
I bought a sound card with optical port, with which I use
I'm not talking about a sound card on the motherboard
Listen,,, I understand in computers ever since I solve every problem alone without help and technicians
The sound card works fine and encoded also seemed to work well I see when I start the software everything works
But somehow it does not convey the information and it happens only with windows 7
In conclusion I can see visually that everything works fine and I also hear the stereo sound
Only 5.1 not working
I use the K coded LITE They work great with WINDOWS XP I really hope we can find a solution will also work with 7

Do you have 5 speakers, 1 bass and 4 surround which don't work? That's what 5.1 is.
Did you try Windows update?
What is meant that the sound card is encoded?

How to explain this
I have a home theater system receiver that I have connected 5 speakers
Until recently everything worked fine I connected the computer via the sound card we are talking about this receiver and I saw MKV movies and all sorts of other movies and it worked great with WINDOWS XP
The day I installed Windows 7 does not work anymore
Now understand the problem?

OK, it is clearer now. You have a sound card with an optical output, your receiver indicates it is getting 5.1 sound but does not play it with the optical output? this worked with this arrangement in XP and not 7?

Is there an adjustment you may need to change within the receiver to accept the optical signal?
I have also asked other Gurus for help and hopefully someone can help you.