I am setting up a PC for a friend to use and all is OK except the sound. When booting up the Windows sound scheme plays perfectly but when playing anything 'external', ie, a CD or a movie or a piece of music copied onto the hard drive the playback sounds like a cracked record, jerky and misfiring. I have reinstalled the onboard Intel sound card driver a few times and tried different drivers but to no avail. Any suggestions. The PC is a basic Celeron 1.3GHZ with onboard sound and video.