My computer has no sound, how do i restore it ? help.?

My computer is fairly old, Microsoft Windows XP Professional version 2002(HP d530), all of my sound devices have got yellow exclamation marks next to them and it says that they are missing or corrupted, I have tried to reinstall drivers from the HP website(didn't work) Ihave also tried to uninstall them and reinstall them(didn't work) I am not very computer literate but could someone please help me out with some step by step instructions on how to restore my sound please, oh yeah and what is reebooting and how is it done. I feel really ignorant and foolish should I just pay a professional!!