Computer does not output any audio.

Hi, my brother's pc (which I'm using right now) does not output sound, and says that there is "no audio output device installed", even though I've checked on device manager and the realtek HD audio driver is installed, running, and as far as windows knows, it is updated. I've tried rebooting the driver and service and still nothing. I've ran AVG a couple of times and the outcome is always the same: No viruses and Malwarebytes Antu Malware says the same.
When I log on, Dolby Theatre says that it doesn't have a driver installed and can't run, that may be the source of the problem but I can't find the driver for this* pc!

I'm guessing this is the result of careless web browsing by my brother, since it is not the first time he has had problems with his computer, but this time the situation is more serious than the usual "my pc is slow/I tried changing my facebook appearance and now my internet doesn't work"

Also: Even though this computer is connected to a wi-fi network, the taskbar icon says that it is not connected and that there are wi-fi networks available. But this is a minor problem, since I'm able to access the internet without any problems whatsoever.

*This pc is a Sony Vaio SVE14A1S1EB, running the original Wondows 7 Homepremium 64-bit.

A Guy- Oh yeah,I forgot to mention, there are no system restores.
I've ran troubleshooter and it says the same thing, that no audio uoutput device is installed.

The speaker does have a red X on it and if I right click it, none of the options are "open volume mixer" so, yeah, no help there.

ICit2lol- I actually haven't tried sfc /scannow, but I am now running the command.
I've already reinstalled the Realtek driver, downloaded it from the Sony site, and that didn't solve anything. For some odd reason sony does not provide the Dolby driver, and neither does Dolby, only lenovo seems to have that driver available for download for some odd reason...

I'm downloading and running now the recommended programs, thanks for the sugestions really appreciate it.

Oh, and abou the specs: The toshiba build is my personal laptop, a toshiba satellite a-something, but I'm typin this on a Sony Vaio, whis belongs to my brother. But yeah, I messed up my system spec and chose desktop, but it's changed now.

Ok, so I ran the cmd and it says tha Windows found some damaged files but couldn't repair some, and then gave me the path to the log containing the details, but here's the twist: There is no log!

Adw Cleaner didn't come up with anything and neither did Super Anti Spyware


I found this forum and someone who had the same problem said that it was a jumper cable that got lose and needed resoldering. Now, I'm not going to do that because I can't solder that well, but if that ends up being the problem I might take the laptop to the store where I bought it and tell them to repair it because it still has a warranty.

I've scouyred the internet and haven't found any solution, I'm on the verge of giving up and just paying someone to do the job.