Sound still appear at speaker even when headphone was installed

Power output on a headphone socket is not great - depends on the headphone and speaker resistance - have you tried a cheap pair of in ear headphones to see if it is the headphone socket.

Headphone socket does sometimes break like the power socket its one of the most common problems on a laptop.

If so its not difficult to find a new headphone socket or even re-solder the old one - it may be a dry joint!

Are you getting sound through the laptop speakers for a start.
The headphone socket should interrupt the main speakers automatically so there is no setting in sounds and devices in windows that would cause your problem.

Is it a fan noise?

attempt to connect external speakers or headphones. if thet work, your internal speakers are the problem and needs replacing. you may also at least check the sound properties and under playback section, make sure the correct playback device is selected. Normally, it should be the speaker/headphone audio device unless you use digital playvack device.

first of all check if you have sound in headphones if not go to start->accessories->system tools->system recovery and here chose day that you know that your sound was working. If it will not fix it try to reinstall sound drivers, and last hope is in reinstalling operating system. If you have sound in speakers its fault of your laptop speakers and you need to change them.

check the corresponding drivers

you may want to try and reinstall the driver from the manufacturers website. I had to do that with a brand new notebook as the speakers didn't work when first turned on. I'll see if I can locate a link and post again if I find it.

I have compaq presario c773tu laptop .I can not find sound driver on internet.

Believe it or not, not all speaker plugs, even if they are of the same size are NOT made the same.Some times the "male" PLUG pushes into the "female" socket in such a way that it makes NO connection or does not make the right connection causing the headphones not to work.
TEST: play music that u can hear through the internal laptop speakers, and while the music is playing, plug in the headphones.
The internal speakers SHOULD cut out, and under normal conditions the music should pass through the headphones.
If the speakers cut out and the headphones don't work, your plug is damaged.
If the speakers DON'T cut out after u plug in the headphones, your plug is open.
Depending on the audio circuit, your audio amp. inside the laptop is going to get damaged.
It depends on the WAY the audio circuit was made.

there is no sound in my laptop

I had the same problem with my Acer 5570 and I just fixed it. What I did is to go to Control Panel > Sounds And Audio Devices >Hardware >On Devices click on Reatek High Definition Audio >Click Properties > On Devise Usage choose the option Do not use this devise (disable) > click OK >then plug in your headphones, click on Realtek High Definition Audio properties again and click on Enable Devise **with the headphones plugged in**. It worked for me.