Adding Space to Another Partition

I have dual-booted Windows 8.1 and Windows 7. I have managed to free up a significant amount of space on Windows 7 and was wondering if it's possible to add some of the freed space to my Windows 8.1 partition?

If pic won't resize, cope and paste: "http://puu.sh/4WcFx.png"

How To Shrink & Extend Volumes Or Partitions in Windows 7

But you should fully defragment your drive first, since the free space could be littered with file fragments which causes the shrink to not show a lot of space.

I assume you mean each partition? Because since I split the HDD into two partitions I can only defrag one at a time.

You only need to defragment the partition you want to shrink. The partition that will be expanded does not need to be defragmented.