Command Option P R not working with Bootcamp installed I have an error 43 when trying to delete a folder in Mac OS - I have read that to fix this I need to reset the NVRAM - to do that I need to boot with Command OptionP R - however, this makes the startup noise continually until I release the buttons.

So far so good, but when I do release (I tried after 2 and after 3 startup sounds) - it just boots directly into Windows.

How can I make this work?
Resetting the NVRAM won't make your Mac boot into OS X, which is what I am assuming you want to do.

What you need to do is hold down the Option key when booting and then select the macOS partition as your startup.

If you want to boot into macOS from Windows directly, you have to right click the Bookcamp icon and select "Restart in OS X"



For more info, please see Apple's Bootcamp Documentation