1. Is your speaker still making a sound if you connect it to a different device?
If yes, that means your speaker is still working
If no, that means that the speaker is dead

2. Have you tried connecting an earphone/headphone/different speaker to the computer? What's the result? Can you hear anything from the other speaker/earphone/headphone?
If yes, that means either the old speaker is dead or the cable connecting your speaker to the PC is faulty
If no, that means the onboard audio in your PC is dead, you need to buy a soundcard. Either a USB or a PCI-e soundcard