Have you updated your Windows XP lately? If not, that is your problem. There are many "plugs" that Microsoft have created to plug the holes in Windows XP.
One of the holes will constently sent out infomation to broadcast that you have an open hole.
This is going to be a pain until the update process is complete. With a 56K modem plan on spending at least several hours downloading and updating your system.
Just in case you don't know how to do this, you open your internet connection. Open Internet Explorer and click on Tools -> Windows update. Walk through the steps to update. Start with the Critical Updates and Service packs before anything else.
And keep updating until all of the Critical Updates are complete. That should do the trick.
OR...if you already do update your Windows XP automatically or for that sake your virus software definitions, then you are downloading the software updates. That is what you are seeing, the bytes count of the downloading Windows update or virus definitions. Let your computer idle for a while to allow the download to finish.
Hope this helps.