Need to add the mbr to windows 7…?

I have a multi-boot, xp and windows 7. XP was installed on one drive and windows 7 the other. I am not wanting to use the XP build anymore. Problem is the mbr is on xp, if I unplug xp then I can’t boot either. I tried the install cd, chose repair system, selected the cmd prompt and did the bootsect /nt60 C: /mbr. That did not work. Any way to make this work without a reinstall? Thanks.