Help?! Computer sound problems?

i dont have speakers for my computer , but i use earphones , sometimes when i started my computer , the sound wouldnt work & id have to restart it & it worked again , but for like a week now , it wont work , & there is usually a speaker symbol at the bottom right hand corner to adjust the volume & it isnt there anymore , i went to my control panel & went to the sounds , speech & audio devices & it wont let me click on any settings because it says "No audio devices" , how can i fix this ? btw i have a dell computer .