After window xp software installation sound could not be heard.

You most likely need to install sound drivers for the sound hardware. Go to http://support.gateway.com/product/?cmpid=topnav and select your laptop from the list and look for "sound drivers". Download the driver to a location on your hard drive like c:sound. Open the archive or exe file and uncompress them to c:sound. There may be a setup program for the driver when you download it but if not, then right click "my computer", select "properties", then "hardware", then "device manager". Under "sound, video and game controllers" you should see a yellow "!" symbol, sometimes several of them for your sound card. Right click the audio device and select "update driver". Browse to c:sound and locate the driver, usually with an .inf extension. Do this for the remaining sound devices and your sound system should be working.

The software that operates the sound card is not part of the XP program, you must go to the Gateway support site and download the sound card software there, it is free. You look up the needed software by model number.