i have a computer tower and the speaker is missing,can i buy one and install or do i have to take the computer to a shop,i really don't know what to do...thank you.

Most PC's or laptops these days don't utilize the internal 'speaker', previously used for DEBUG and low-res sounds for some games.

Sound is now handled by 'Stereo or Multi-Channel Sound Board', or embedded on the Video-out Connector.

Some systems, like laptops, will have internal Stereo Speakers. Most all systems will provide Sound-out via minijacks so you can connect your own earphone, headphone or connect to an external amplifier (or amplified speakers).

If you think you need the deprecated internal speaker, take a look at your Motherboard and see if it has a two-pin header with SPK or SPKR. Most any 8ohm mini speaker will work with that.

Your machine will work just fine without the beeper, you just won't hear the startup diagnostic beeps.

Any place that builds machines should be able to supply a spare beeper for a nominal fee.