NTLDR is missing

I am trying to fix a machine with the error "NTLDR file is missing."

I do not have the owners original XP boot CD, but I do have my own XP recovery disc. After reading some of the other answers on EE I've come to the following solution to try: Posted previously by Nubos:

"here what you need to do :
Boot using the Windows XP installation disk, press R. Then type the following commands:

      FIXMBR
      FIXBOOT
      BOOTCFG /rebuild
      cd\
      copy E:\i386\NTLDR
      ATTRIB -arsh ntldr
      copy e:\i386\NTDETECT.COM
      ATTRIB -arsh ntdetect.com
"

I logged into the recovery console using my disk, and when I went into FIXMBR I received the caution message about "this computer appears to have a non-standard or invalid MBR. FIXMBR may damage your partition...etc.

Is this still the option that I want to use? I don't want to damage this machine any further. The caution and "non-standard MBR" warning kinda scared me off.

I also went into FIXBOOT but did not run the command.

I guess I just want to make sure that this is the correct solution for this issue and that I can use MY disk to recover the files without damaging the machine.

Also, there is no floppy or CD in the respectable drives. This is a Dell Dimension 4600.

Thanks!