how dos prompt available in NT?

I have to modify some files in winnt folder. The system don't permitt
to modify these files when NT is running, so I have to have dos prompt
available just after turn on the pc, before windows comes. I've tried
with NT boot disks, but the installation procedure don't let to go to
dos prompt. I've tried with win9x boot disks, but it don't recognise
the drive "c:" (probably beacuse is not FAT32 formatted). How can I
modify the system 32 files?
Thanks

 

There are DOS utilities that allow you to read NTFS partitions but maybe we can take a different route. What files in the WINNT directory do you need to modify?