No audio device.

Hello.

Yesterday i reinstalled my windows , instaleld all the drivers , everything working good , no problems... After 2-3 hours when i wanted to listen a song on youtube it wasnt working , i checked the audio tab in the control panel and it was saying ,No audio device' but i could hear my friends talking on skype. When i ran services.msc and started the Windows audio thing it was working again , how i can set it to keep it running without stopping ? Its boring .. By the way , i didn't reinstall my driver again , im too lazy ^^.