In WinXP, in C:\WINDOWS\, u will find a text file named "0". If you open it, nothing is there in it. i wonder what its for. its always there, and pops up back, even after you keep deleting it ! anyone know !? 
what is c\windows\0 in Win XP !?
its just a log file, its harmless. i just searched google and read in this page that its used by win xp during startup. so no need for any worries. 