My sound will not work!!! ;-{

Hello,

I have a Hp slimline pavilion s7627 i kno its kinda old and my sound card is the realtek high definition audio something like that. when ever i try 2 play music in win media player it says Windows Media Player cannot play the file because there is a problem with your sound device. There might not be a sound device installed on your computer, it might be in use by another program, or it might not be functioning properly. and when i try to test my speakers it says failed to play test tone. Ive been to the site to download a new driver doesnt work. I uninstalled my current driver and installed an older one doesnt work because everytime i reboot it installs the driver i just uninstalled. PLZ HELP!!! Ive had this computer since Korea n Iraq n shes my baby. O yea and i use Vista