No, there's no way to undo this except to simply redo the installation.
Next time be a little more careful that you don't "accidentally" reinstall the OS. Something that seems like it takes a number of deliberate steps to accomplish, so I don't know how accidental it can be... But it doesn't really matter now, because it's done, and you're stuck with the consequences.
ok i accidentally re installed windows xp is there anyway to undue it
because all of my programs/software r missing
some of my old files such as videos mp3 are in desktop/documents and settings/etc...
but what i really want the most r the my old software/programs/drivers
so is there anyway to reverse this please someone help asap