Are you referring to the basic scene file or are you caching the scene? The basic scene file won't take any longer than normal to save, XP doesn't save much extra data into the scene over and above the objects. So it's unlikely to be due to XP in that case. What is the scene file size in your case?
If you are caching the scene this can take a considerable time, depending on scene complexity. The actual file save is not slow unless the files are gigabytes in size, but the caching process can be. If you cache internally then save the file, that can result in a very large single file, which would be slower to save, so we'd recommend using external caching unless the scene is a simple one with low particle counts.
But as I say, absent caching file saving should be no slower than any other file.