bilfiore--
Per Amazon's website,
http://www.amazon.com/gp/feature.htm...cId=1000426311, the Kindle for PC still works on Windows XP. It seems that there is something going on on your PC that is conflicting. That being said, it's a good idea to upgrade from Win XP if possible. Microsoft quit supporting that, including offering security updates for it at the beginning of this month.
Good luck--and I hope you can get Kindle for PC working for you.