[NFBCS] Accessible way to mark partition as active outside of windows?

[Blake Hardin]

Hi all, so I have a duel boot system running windows 7 and Windows XP.
Yes yes I know, old lol. But I was going to delete my windows xp
partition and install windows 7 and upgrade to Windows 10. That way I
will have windows 7 for older applications if needed. So I went and
marked windows xp as inactive so that I could delete this partition.
Windows 7 was also marked as active so figured it would just boot to
windows 7 automaticly. But now of course it says can't find operating
system. Ug. So what program can I use that may be accessible for me to
mark the partition as active again? I did not mess with the windows 7
partition so it should still be set to active. Bart PE maybe? Or any
other easy to use things that are accessible? Thank you.