windows - OEM partition of 465 GB in a 1TB disk, too big - how to resize it?

I just bought a new computer and I installed a windows 8 and I would to install a Windows Server 2012 in another partition in my PC, but there is this OEM partition that is occupying half of the computer disk. I didn't want to delete it, but to resize it, if possible, 456 GB is too much in my opinion.

Here is a picture of it:

Answer

Download gparted from http://gparted.org/

boot into it. use it to resize the partition.