Need help on sound issues.

So a while back I had vista installed on my laptop, Acer 6920, (first OS) and it was direct from factory so everything worked fine. I then installed ubuntu and everything still worked fine. I then deinstalled both of those to put on windows 7 RC where all my hardware was working perfectly (minus the fingerprint reader but i honestly couldnt care about that thing) so my computer eventually got pretty bogged down with crap to the point where boot was about 30 minutes. during this whole time my sound seemed to work, but near the end windows stopped finding any internal sound related hardware (the speakers and the mic). For other reasons i did a clean reformat (3 times) and reinstalled 7 Professional 32 bit and when i booted i downloaded all the drivers and everything seemed to install correctly, but when i rebooted the sound still didnt work nor did the mic. the exact error message windows is giving me is "No Audio Output Device found" however when i plug in a headset or a bluetooth adapter + headphones there is audio and it works perfectly. I really need sound to work as some programs crash if they dont detect a sound output and also for monitoring audio recordings.
I have tried installing all of Realtek's drivers. Literally all of them. None of them worked what so ever despite clean installs and deinstalls.
I now am running 64bit and ive almost given up on this problem. I bearly saved this computer and i dont wanna have to buy a new because of sucha stupid issue like this.
More info:
Under the hardware manager in windows there is no tree for sound devices. there was an unknown component which i put forceware on as i thought it was the sound device but no go.

DXDIAG:
Operating System: Windows 7 Ultimate 64-bit (6.1, Build 7600) (7600.win7_rtm.090713-1255)
Language: English (Regional Setting: English)
System Manufacturer: Acer
System Model: Aspire 6920
BIOS: Ver 1.00PARTTBL6
Processor: Intel(R) Core(TM)2 Duo CPU T7500 @ 2.20GHz (2 CPUs), ~2.2GHz
Memory: 3072MB RAM
Available OS Memory: 3070MB RAM
Page File: 1303MB used, 4835MB available
Windows Dir: C:\Windows
DirectX Version: DirectX 11
DX Setup Parameters: Not found
User DPI Setting: Using System DPI
System DPI Setting: 96 DPI (100 percent)
DWM DPI Scaling: Disabled
DxDiag Version: 6.01.7600.16385 64bit Unicode

I would really appriciate some help on this... ive been trying for months now with no solution. forceware, updated drivers, reformating... none of it worked... help!

 

Bump? pleasee....

 

Did you try reinstalling vista and end up with the same issue?

 

That is some seriously strange stuff.
How on earth did you let your system get bogged down to a 30-minute boot time?!
Test other OSs - Vista, XP if you can find it, Linux (I personally found Linux Mint had working sound out of the box, something Ubuntu didn't) - and see if they come back with the same problem.

 

As a quick non-destructive test Use a bootable linux Disk like knoppix. How long does that take and does everything work?

if it did and you want to sort out W7 :

Do another clean install, reinstall windows 7 from a retail disk, make sure you install all the chipset, AHCI, launcher, graphics, communications and audio drivers that ACER supply even if you have to use vista ones initially. don't worry about the apps for now See how that works. Long delays at startup can be the result of disk drive or missing/wrong driver problems

 

So, I've tried everything at this point.
@ EntityX
I hesitate before even touching that OS, but at this point that may be the last thing i can try...
@TehSuigi
I have, I even tried installing iAtkos, and everything worked but the sound. XP, Redhat, Ubuntu all that jazz. Sound doesn't work in any of them.
@BruBoo
Those things all work, it's just the sound. The bootup issue was solved by 3 reformats (over kill yes, but its better to be safe than sorry).


All in all, I think Vista is my last ditch effort before I finally succumb to the horrible idea that I may in fact, have a hardware issue on my lappy. Well, lets see how this goes. Thanks to you guys for all your ideas. I'll probably tear it open if Vista doesnt work and ill post how it looked internally and all that stuff.... thanks again.