No sound On machine after installing Ubuntu

Hello there

I have installed Ubuntu on my pc that had windows 7. But now I can hear any sound from my pc's internal speakers. Can some one help me.

So you have installed Ubuntu in dual boot with Windows 7, great! Anyways, for your problem, here is a solution. Go to System->Preferences->Sound. Now make sure that each item here is checked to appear in the mixer. Make sure none of them are muted. Now go to "Switches" tab. Look for "External Amplifier" switch and set it to off.

I have only Ubuntu on the PC and I'm new user to ubuntu. I have not seen the "Switches" Tab