You have to do it on the drive with your "boot" partition. For me, the drive letter was G:. So I had to do. CD G: Then CD boot. Then enter the command. bootsect /nt60 SYS. Try changing to C, D, E, or whatever. Maybe just type DIR to see if you can find the "boot" directory.
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You can also try this;
I also fixed the problem on one machine which would try to boot but not start at all, it just started the grub loader and stopped, ( because there was no longer a Linux partition on it).
I took out all the drives except one and tried to boot from each one. When I got the error ( on the third try), I formatted that drive on an XP machine, and then replaced it. Everything worked after that.
Just ideas which may or may not work with your specific problem.