How can I undo “mark partition as active” using GParted/Linux live CD?

In the process of trying to shrink my hard drive partition, I marked my C: drive (the only drive I have) as “active” in Windows’s “Disk Management” software. When I rebooted, it said something like “boot device not found” (can’t remember the exact wording).

I can’t boot into Windows, but I do have a Linux Mint cd that I’m on right now. From my research, it looks like the equivalent of “Disk Management” is GParted.

So the question is, how can I undo marking the partition as active (within Linux) and be able to boot into Windows again?

Right now GParted looks like this:

Solution 1:

It's the same flag. The "active" flag in Windows is called the "boot" flag in Linux.

Windows and Linux use different terminology for the same bootable partition or drive

The term "active" is used for the bootable partition when you are in a Windows/DOS-type environment.
The term "boot" is used for the bootable partition when in a Linux environment.

http://thpc.info/how/make_active.html

You can modify the flag in GPartEd by right-clicking the partition and selecting "Manage Flags". To undo the boot flag, uncheck it with the C: partition and add the boot flag on the System Reserved partition.