|What does the sound card entry in device manager look like when the sound disappears? Black exclamation mark on yellow background or red X next to it?|
First thing to try is uninstalling the driver again, only from safe mode this time and then reinstalling the correct driver - from safe mode.
So if you can find the last sound driver update for your Compaq Presario model, download it to your desktop and use that, and install it from safe mode.
And if it continues after that, then something is breaking the driver, so have a think what's different, what's new, anything newly installed since the problem started, etc.
Could also be a malware issue, so think if you have any other issues / error messages / behaviour rolled up with this one. But I would work through the basics first before looking further afield.