2 window xp O/S on same computer ?

I reformatted my computer and i realize when i was done there was two(2) O/S "WinXP Home Edition" (twice).Is there a way i can delete one of the O/S, without having to delete all partions & start over again by reformaing it???

I really don't want to have to reformat it all over again, I hope some one knows how to do this without any future glitchs happening later?
Thanks in advance