Windows 7 boot option disappeared

Hello everyone!

I hope apple community will help me with my issue.

Long story short, I have 2 hard drives installed on my mac, one for mac os and the other drive had 2 partitions one for windows and the other for my files just for storage. 2 days ago I upgraded my Macbook Pro mid 2012 from El Capitan to High Sierra. After upgrade my Windows 7 worked perfectly with Bootcamp, when I restarted my mac and hold option key windows 7 was there and booted fine.

Yesterday I opened my disk utility app and found some unknown partition using 102 gigs, I couldnt remember what is was so i deleted it (it was on my hard drive with windows and storage) after i tried using windows 7 it disappeared as an option only MacOS.

I can still access my windows files on finder but cannot boot Win 7.

Please help!!!