Q: Mac No Bootable Device

Do you have another Mac?

1. It is possible that Windows installation formatted and overwrote the Mac firmware. Can you boot into Windows ?

2. Do you have Yosemite Installer on an external disk?

If Windows is bootable, can you download GPT Fdisk from  http://sourceforge.net/projects/gptfdisk/ ? It will download two binaries gdisk64 and gdisk32.

Here is an example of running Gdisk on Windows. You need to run this in Windows in a Command Window with Administrative privileges. The link at the bottom is a tutorial for Gdisk. Post the output of the 'p' command as shown.

C:\Users\MyName\Downloads\gdisk-windows-0.8.10>gdisk32 0:

GPT fdisk (gdisk) version 0.8.10

 

 

Partition table scan:

  MBR: hybrid

  BSD: not present

  APM: not present

  GPT: present

 

 

Found valid GPT with hybrid MBR; using GPT.

 

 

Command (? for help): p

Disk 0:: 500118192 sectors, 238.5 GiB

Logical sector size: 512 bytes

Disk identifier (GUID): 22749ACF-207D-458E-B255-5DF02C39DC2D

Partition table holds up to 128 entries

First usable sector is 34, last usable sector is 500118158

Partitions will be aligned on 8-sector boundaries

Total free space is 1325 sectors (662.5 KiB)

 

 

Number  Start (sector)    End (sector)  Size       Code  Name

   1              40          409639   200.0 MiB   EF00  EFI System Partition

   2          409640       250801735   119.4 GiB   AF05  OSY-MBP13

   3       250801736       252071271   619.9 MiB   AB00  Recovery HD

   4       252071936       500117503   118.3 GiB   0700  BOOTCAMP

 

 

Command (? for help):

http://www.rodsbooks.com/gdisk/walkthrough.html

What is the exact year/model of your Mac? Does it have an Optical drive? If it does not have built-in Optical drive, do you have an external Apple SuperDrive?

Is there a built-in Optical drive?

On the bottom cover of your Mac, the serial number should be etched. Use https://selfsolve.apple.com/agreementWarrantyDynamic.do and put in the serial number and you can post the exact Model year. You do not need to post your serial number on the discussion.

Please also see how to Find the serial number of your Apple hardware product - Apple Support.

Can you try to boot Windows in Safe Mode?

At this point my recommendation is to find the nearest Apple Store and get a Genius Bar appointment. They have the ability to erase and re-install OSX and boot from external media.

http://www.apple.com/retail/geniusbar/