would like to know the answer to this myself for reference. a friend of mine had exactly the same problem a few months back after purchasing a second hand computer from a local company. it came with windows '98 starts here edt' what ever that is and it displayed this error, requested these files 'kmixer.sys ksuser.dll stream.sys' when he tried to install a new c media soundcard.
tried all the usual sfc and downloading the files needed didnt make any difference. could not re install windows 98 from the disc supplied so he purchased a new pc with xp in the end.
sorry i cannot help.