Sometimes sound works and Many times no sound

Hi,
I have Win 98 Second Edition, 166 MhZ Pentium PC. Bought
it 7 yrs back.
For the last 1 year I have a strange problem. When I
switch on the computer sometimes the opening windows
welcome sound etc will play and I can even play songs
(using winmp or windows media player) but randomly many
times the welcome sound doesnt play and also if I try to
listen to songs no sound will come. In those times
of "deaf/dumb" situations the volume controlbar icon also
doesnt get displayed in the taskbar. (When sound works it
get displayed).
If I go to control panel and click on Multimedia in the
Audio tab I get playback and Recording but both of them
are grayed out. In both I get the following 4 optons
within the drop down", "Game compatible Device", "Voice
Modem Wave #00 ine" and "Voice Modem Wave #00 Headset".
Again both of these have one more option "To select
advanced options, Click Advanced prperties" But this
Advanced property option is greyed out.
Also, the option "Show volume Control taskbar" is greyed
out.
If I go to devices tab within Multimedia properties then
within Audio devices I get a single option "Audio for
External conexant Voice modem serial wave device".
Within the Midi Tab everything is greyed out and cant
select anything.
If In control panel I go to sound then If I click on let's
say Asterik option then I cannot listen to the preview as
it is greyed out. Same case of not being able to preview
any sounds
Please note this whole thing is random. Sometimes Im able
to listen and experience sound (20 percent) and 80 percent
of the time it just doesnt respond. Even when it works and
if I listen to some songs then some error or something
gets displayed after 45 minutes or so and it stops working.
I have many times formatted my C drive and reinstalled
evrything but to no avail. I have already gone through KB
article 183087 but it doesnt seem to apply to me as when
the sound works fine then Im able to play around with the
buttons in the multimedia icon within control panel.
Please suggest a solution.
Regards,
Hari
India

Check in Device Manager, and see if there isn't by
anychance a problem with your soundcard. Then you might
want to try reinstalling your sound card drivers. If the
computer was moved recently, maybe the sound card came
loose inside the pc.