file Msisys.VXD & corrupted C-Mixer,speaker cone gone

My pc recently has been either trying to crash, or
something inside is eating my Msisys.VXD file. I
constantly have to go to file checker to get it back
every 10-15 mins. I have tryed everything, & searched
everywhere, to no avail. Can anyone help me please?
This is a fairly new pc, & was built for webmastering &
music, being home bound, it is a very important part of
my life.
Also, I don't know how or why, but my C-Mixer icon is
here on the desk top, but won't work & my speaker icons
(yellow cones) have disappeared?
Please help me if you can, I have ran out of options
as to what is going on, & what to do.
I did run all my anti-virus & spy ware...my pc is clean. I
thought it was a virus, but now I don't know what is
going on.
I appreciate any help.
Thank you,
Judy (pulling her hair out!