More than one bootable primary partitions
I have three partitions which I've created in cfdisk and want to write. I have a primary, sda1 with Windows on it, and two logicals, sda5 - my swap partition and sda6 - my Linux partition. I've made both my Linux and my Windows partition bootable.
When I select write to write the changes to the disk, it says that more than one primary partition is marked as bootable and the DOS MBR cannot boot this.
Just wondering if it had actually written the changes and if this mattered? What is DOS MBR?
Thanks very much!