The My Book World Edition uses an ARM processor and is not capable of running Windows Server.
From Wikipedia:
This drive runs linux on an Oxford Semiconductor 0XE800 chip which is based on the OXETHU954 chip. This is an ARM based chip. In addition it uses a Via Cicada Simpliphy vt6122 Gigabit ethernet chipset, and a Hynix 256 Mbit DDR Syncronous DRAM chip. The webserver is the lighttpd server.