As we are limited to four primary partitions on an MBR disk, or three and an extended logical, and as I want a multiboot setup I need to remove at least one primary and preferably two.  Looking at my System Reserved partition it contains only a log file, which seems to me rather a waste of a primary.  I think I could also dispense with the Recovery partition as I have a whole of disk backup as it is now.

Any reason I shouldn't just remove both?