Audio and sometimes video doesnt work?

My audio doesnt work after i got a virus. I removed the virus by downloading Malwarebyte's Anti-Malware. I had the Trojan virus. After it got removed I now have no audio.It says im using Realtek digitil output, in my Systray. and that the volume is at 100. I have Windows XP im pretty sure. HP Desktop.

I went to control panel - Hardware and sound - Sound. When i go to adjust system volume it says a bit of sound if is being heard, but i dont hear anything. When i go to change system sounds, it still shows a bit of sound, but i dont hear a thing. When I Mute the sound, my volume mixer just freezes on me.

My sound comes out of my Computer Screen. What do i do? I will provide more info once i know what to say.

Also, when i test my sound, i hear nothing. When i go to device manager, it says Sound, video and game controllers - Realtek High definition Audio Properties. It says the device is working properly, but it isnt. Help please?

If i have to go to a computer, where do i go? I have Best buy and future shop around here. But what do i say to them? and if i have to remove my soundcard, how do i do that?