|You probably need the upgrade disk rather than a full version.|
When going from 95 to 98 or 98 to 98 SE or when doing an 'over the top' reinstall with those versions you could just rename win.com to something else and do the install using a full version disk, making sure the install went into the existing directory. I think that worked for ME too.
But I don't know (and kinda doubt) that will work when upgrading to XP. So I don't recommend you try it unless you verify from other sources that it will work.