Dont know about going missing after a defrag but ur NT Loader, can be missing if u install another O/S .....dual boot u have to check ur boot.ini u can replace it by following this: In the i386 directory of the CD-ROM there will be a file NTLDR._, which is the compressed version of NTLDR. You can expand this file using expand.exe that comes with DOS and Windows for Workgroups expand d:i386ntldr._ c:ntldr. make sure u boot ur puter first in dos