sound problem with windows 98

windows 98 will not correctly play any of its sounds. Sound is present but so jittery or stuttered that it is unrecognizable. I have uninstalled all sound card devices in device manager and rebootted but this did not fix it. Playing sound from control panel give same result. I have down loaded new drivers but this did not work either. I have upgraded my computer from 75MHz pentium to 333MHz overdrive processor, added a 56K modem, and USB port. It is an HP Pavillion 5030 w an Intel advanced MN motherboard. This problem is present even though device manager shows no problem with hardware. How can I fix this problem? My computer occasionally hangs on shut down which may be related to this sound problem.