My pc dont have a sound driver - MSI /Micro Star NX7800GTX-VT2D512E GeForce 7800GTX 512MB GDDR3 PCIe Retail Graphics Card Graphic Card

Is easy. you need software/driver for your sound hardware.

how to find?

Find your model and name for your speaker.
if you know, then you easily google for it.
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if you dont know name and model.. Open device manager
if you dont know, click here. choose your operating system(os) that you use now(current os)

Example picture show the problem hardware
can you see it?. Icon with yellow color in question mark that your hardware have problem with driver. Try to right click and once window will pop up.
Find driver tab. And update, It will need more time depending your pc/laptop.
If you dont have internet connection with that cpu, then you can find a google using other pc/laptop with internet. type your's device/hardware name/model +driver at google.good luck

dont worry dude just downlaod iduble driver scanner softwrae...

Check the device manager and see if the driver is currently installed. Also watch out for a mute button on your laptop. People press it all the time without relizing

http://downloadcenter.intel.com/

Motherboard Sound Drivers for model: AWRDACPI No sound at all after I format my PC.I dont have my mother board CD with me .Please find me a solution for me.My System Manufacturer (GBT_),System Model (AWRDACPI)

what make and model computer and does it have on board sound or separate sound card you will probably need motherboard drivers as well soon as I know I will get the web address so you can download them

You can try download your driver as below link :

http://support.creative.com/downloads/download.aspx?nDownloadId=1843

to check the sound driver -
click start - right click my computer - properties - device manager then look down the list and see if there is a yellow ? beside sound, video and game controllers. If this is the case first try to update the driver there otherwise go to http://support.acer-euro.com/drivers/notebook/as_4520.html
Hope this helps

After I have formatted my computer, there is no sound out of my computer. I want to get sound driver,but I can't find one.

What modelof your laptop, I'm confused which was your laptop.