Can't expand a partition

I'm running a Mac Mini with Windows 8 on it, and I've got an external hard drive which stores steam games etc. I've found out that I use Windows 99% of the time, and therefore don't need the partition allocated to OSX anymore. However, I can't expand the partition in disk management, as the extend/shrink buttons are grayed out. Keep in mind that the partition is primary, and it's healthy as well.

Thanks.

 

There is no windows files on there, only steam games and other programs. The disk I'm trying to expand is the second one, of which half of it is not allocated. I've now made a new partition, and am hoping to merge the two together. EDIT: The program that I was going to use (EASEUS PM) had corrupted setup files, so I'm now trying to find something that can either expand partitions or merge two together without formatting either