How to clean boot menu and check/clean mbr

I had successfully installed Windows 8 Consumer Preview on my mac mini (bootcamp install) but Windows crashed during the upgrade to Release Preview and I removed it a result. But there seem to be some traces of it left.

How do i remove the efi boot entry from the mac's boot menu. I managed to mount the efi partition and deleted the windows folder in it but i still get an efi boot option when I press the option key at startup (of course selecting this entry does nothing now). Is there a boot menu file with the default entries ?

When I try to install windows 8 release preview with bootcamp again (bootcamp does the partition, creates the bootable usb key from the iso and download the windows software) I get the error message :

"The selected disk has an MBR partition table.  On EFI systems, Windows can only be installed to GPT disks"

Yet I see no mbr partition, so I assume there must be some traces left by the windows installer on the mbr of the disk. Is there a way to clean it up ? Or does the error message come from something else ?

EDIT : bmike's suggestion worked

Solution 1:

Credit goes to @bmike for answering this one, but I wanted to answer it here so the question is closed. Marking as community wiki so that I'm not taking credit.

In this situation you will want to use the recovery tool built into the system's firmware, called "OS X Recovery". You can read Apple's documentation here. To start OS X Recovery, hold Cmd+R while you press the power button to turn on your computer.

This will download a full copy of OS X to install, so you'll probably want to hook your computer up to ethernet if it's at all available.