Slow downloads only from Microsoft

Over the past month or so we have experienced very slow downloads from Microsoft. We have a T1 pipe to the web. We can expect 160+k from sites at 3com and HP but Microsoft comes in at around 4k! I have asked friends in the business around town totry the same downloads and they get at lease 90k. What could be slowing me down for a specific site? DNS seems to be working fine. We don’t have any problems accessing the site just download speed.