Go to computer management (click on the Start Button/Orb, and right click on computer, then click manage).
Click on Device Manager and take a look to see if you have any yellow triangles. Yellow triangles basically mean either an error or driver/device not installed.
If you have a sound card, look at that companies website, or if it is built in to your motherboard, take a look at the motherboard manufacturers web page.
You need to basically find the sound driver which should be on their support / downloads page.
IF however you know the exact name of the sound driver, you may have luck going to the actual chip manufacturers website (e.g. Realtek) and searching, but you won't know unless you know what you have.
As for checking for mute - Look for the sound icon next to the clock and see if it has a cross through it. If you do not see the icon at all, it is probably an indication that there is a problem with sound on your system.
And, sorry, it has to be said - If you see no yellow triangle and the sound icon is there and unmuted, make sure your speakers are plugged in and working.