you should be able to install Windows Server 2003 on that free space. Before you do so, make sure you have created the linux bootdisks because Windows Server 2003 will definetely overwrite the MBR which means that you will have to reconfigure grub or lilo (whichever bootloader you have originally installed).
Since you really need it for a project, I'd say make sure you have created the bootdisks, and you should give it a try. Just make sure you don't select the wrong partition when you install it or remove any unneccessarily
Have you ever thought of using VMWare? You could use it and probably use Windows Server 2003 that way as well - sort of like a virtual O/S through linux. But that's totally up to you.
Hope this helps!