Depending on what you did to clone the disk, you may have changed the boot record of the drive. Sometimes just plugging in the drive to another computer will do this.
If you can get into dos, possibly by loading the NT setup floppies you may be able to get to the recovery console, ifso you can type fixboot and it should ask you if you are sure you want to rewrite the boot table. It's been awhile for me, so I hope I didnt miss anything. Fixboot does not format anything, so it shouldnt mess anything else up.