I've cured it many times by installing a newer sound card driver. I can't help further since I know nothing about your machine. But do ask it's maker.
Ever since I tried DL'ing a sound app to let me listen to a radio station over the net, all streaming audio as well as wmv files sound speeded up. Human voices and singing sounds like Alvin & the Chipmunks. How can I fix this? OS is Windows 2000.