Boot sector restore for FAT16 on dual bo

I got a Windows NT 4.0 workstation with dual operating system boot (Msdos and Windows NT) I want to restore or rebuild the Windows NT Hard disk boot sector I erased by mistake with DOS “SYS” command. It seems that Windows NT installs his own versionof boot sector and do a copy of the Ms-dos boot sector on the bootsect.dos file. The problem is that I replaced the physical HD boot sector and my windows NT workstation can’t boot on NT instead it goes directly to MSDOS.

Does anybody have any suggestions other than reinstall windows NT?