Sudden loss of sound

Hi...my system has been functioning great for 3 years now, I have a Compaq
Presario 5310us system with 40 Gif HD and 256 RAM, I have XP Home Edition
and over a month ago updated to SP2 with no problems.
About a week ago ( I can't remember what I was doing when it happened) my
speakers made weird screaming , popping and squelching sounds. I muted the
speakers. I don't know when the sound went out. My husband swears he heard
game sounds when I was playing Red Faction a few days ago. I went to play
today and no sound. I haven't really noticed the sound being gone until
today ( I tune the system sounds out I guess).
I have checked Devices, drivers, and everything says enabled and working. I
disconnected the speakers and tested them with other audio equipment and
they work fine. I don't know where else to look. Nothing has changed, there
are no new programs, I run virus checks and spyware checks every few days. I
don't know why the sound has just stopped working.
Any suggestions?
( I did delete Yahoo downloaded chat software last week, it's the only thing
I can think of even remotely connected to sound changes)

--
Glenda P

Never mind......... after trying all day to solve the problem, I discovered
that there are 2 audio ports on the back of the pc and the second one works
so I can only assume that the other port is burned out. If this happens to
you, might want to check and see if there are 2 ports on yours before buying
a new audio card ( which I was almost ready to do!)