[CentOS] Reinstall Windows but preserve CentOS

I have a computer that dual boots between Windows and CentOS. Each has it's own hard drive.

I suddenly have a problem with Windows, and may need to reinstall. I need it for applications like After Effects, Premiere, and other things that I am currently in the middle of a project with.

It seems the system has become usnstable, it's preventing me from continuing to work, and I may need to wipe the Windows partition clean and start again.

My concern is that if I do that, I will lose the Grub boot loader and not be able to access CentOS again.

How can I reinstall Windows with a clean partition, and preserve my dual booting?

Dave