to install windows 8 or 7 on mac pro (10.9.5)

Howdy rbannaii,

It sounds like you are wanting to install either Windows 7 or 8 on your Mac. Since I do not know specifically what resource you were using before, I would recommend the information in the following link to help you get Windows installed using Boot Camp:

Boot Camp Help: Install Windows on your Mac

Here are the initial system requirements and preparations that need to be made, and once everything is verified, click the link and follow the instructions in there:

Install Windows on your Mac

With Boot Camp, you can use Windows 7 or 8, or OS X on your Mac.

To use Boot Camp, you need the keyboard and mouse or trackpad that came with your Mac. (If they aren’t available, use a USB keyboard and mouse.)

To install Windows using an installation disc you need the following:

• A built-in disc drive or a compatible external optical drive.

  For information about using your Mac with an external optical drive, see the documentation that came with your Mac.

• An installation disc with the 64-bit version of Windows 7 Home Premium, Windows 7 Professional, Windows 7 Ultimate, Windows 8, Windows 8 Pro, Windows 8.1, or Windows 8.1 Pro.

  You must use a single full-install Windows installation disc. You cannot use an upgrade version of Windows.

• An external USB drive formatted as MS-DOS (FAT).

  After you install Windows, you need to install support software that lets Windows work with your Mac hardware. You can download the support software to an external USB drive. To format an external USB drive as MS-DOS (FAT), use Disk Utility, located in the Other folder in Launchpad.

You may be able to install Windows using an external USB drive that contains a Windows ISO image (a disk image that contains the entire contents of a DVD) downloaded from Microsoft and Windows support software. To find out if you can install Windows using a USB drive, open Boot Camp Assistant, click Continue, then see if the option “Create a Windows 7 or later install disk” is available.

To install Windows using an external USB drive you need the following:

• An ISO image of the 64-bit version of Windows 7 Home Premium, Windows 7 Professional, Windows 7 Ultimate, Windows 8, Windows 8 Pro, Windows 8.1, or Windows 8.1 Pro downloaded to your Mac.
• An external USB drive that is 8 GB or larger.

  Boot Camp Assistant erases the external drive and copies the Windows ISO image and support software to it.

If you need help determining the best size for your Windows partition, refer to your Windows installer documentation. For Windows 8, create a partition that is at least 30 GB.

Thank you for using Apple Support Communities.

All the best,

Sterling

Hi Sterling R!

Best response I have seen so far in regards to searching for help on this issue, plain and simple response, no jargon! However, I am also having the same issue.

I have purchased an online version of Windows 8.1, to which Microsoft has sent me a download link and an exe. format download. However I cannot download the exe file because it is not compatible with OS X. I called Apple support and a technician said Microsoft had to send me a dmg format download, but when I rang Microsoft they said I needed an ISO image.

How would you go about getting an ISO image on an external USB drive?

Thank you for using the Apple Support Community. Due to the nature of your issue you may find more information by using another one of Apple's support resources - https://getsupport.apple.com/GetproductgroupList.action.