Running the iMac with Boot Camp and Win XP on 24" 2.4GHz Alum iMac, I get tons of hiss and swishy sounds when using iTunes (or any other player). Music sounds awful, as if recorded on a cheap cassette recorder from 30 yrs ago. These are high quality carefully recorded ECM jazz tunes. When I play the same tunes in OSX and iTunes, no problems. Sound great. I can't find anyone who has the same problem.