I have a sound problem on my laptop

Hello,
recently i have format my laptop,twice,but the problem is still same.. my problem is when i on my laptop at the beginning the sound appear and i can play any song i like..after that,when i turn off the media player and try to play it again, it can't and no sound appear. the warning says that there is no sound drive and ask me to install it. but the sound from my laptop will comeback when i turn off and on my laptop again. before this, i went to the person that know about this technology and he said that there is a virus that attack my laptop. so i format, but after i format it, the problem is still same. after format, they install me AVG, and then i uninstall the anti-virus and i install Kaspersky Anti-Virus and run the full scan, and after that i found that in my laptop there are many virus..some of it can be terminate, some can block and some cannot do anything. and the virus is in system32. what should i do? do i have to format my laptop again?