Want to use internet recovery to reload ML, but says can't

Question

I've given up on waiting for Apple to fix, or acknowledge the problem I have (and many others) with my BT equipment.
I thought I could just use Internet Rcovery to wipe the existing installation, and reload a fresh (working) copy of Mountain Lion (I do not have files/info on this machine I need).
When I try and  update, it says " OS X cannot be installed on "Macintosh HD" (it said at first "because a newer version exists", but that message is no longer shown)
Am I missing something, all I really want to do not is go back to a working OS

Answer 1

Well, Mountain Lion has been replaced by Yosemite. You can install Yosemite but not Mountain Lion using Internet Recovery. Also, to use full Internet Recovery you will need a 2011 model or later: Computers that can be upgraded to use OS X Internet Recovery.
You should also take a look at: The Worst Bugs in OS X Yosemite and How to Fix Them that includes a possible solution for BT problems.
Install Mavericks, Lion/Mountain Lion Using Internet Recovery
Be sure you backup your files to an external drive or second internal drive because the following procedure will remove everything from the hard drive.
Boot to the Internet Recovery HD:
Restart the computer and after the chime press and hold down the COMMAND-OPTION- R keys until a globe appears on the screen. Wait patiently - 15-20 minutes - until the Recovery main menu appears.
Partition and Format the hard drive:
Select Disk Utility from the main menu and click on the Continue button.
After DU loads select your newly installed hard drive (this is the entry with the mfgr.'s ID and size) from the left side list. Click on the Partition tab in the DU main window.
Under the Volume Scheme heading set the number of partitions from the drop down menu to one. Click on the Options button, set the partition scheme to GUID then click on the OK button. Set the format type to Mac OS Extended (Journaled.) Click on the Partition button and wait until the process has completed. Quit DU and return to the main menu.
Reinstall Lion/Mountain Lion. Mavericks: Select Reinstall Lion/Mountain Lion, Mavericks and click on the Install button. Be sure to select the correct drive to use if you have more than one.
Note: You will need an active Internet connection. I suggest using Ethernet if possible because it is three times faster than wireless.
This should restore the version of OS X originally pre-installed on the computer.