BOOTMGR is compressed.

I have Bootcamp Win 7 as default operating systtem and when I turn on my MacBook Air, it just says BOOTMGR is compressed, press ctrl+alt+del to restart.

No combination of keys makes it do anything, all I can do is turn it off and back on again to the same screen.

can you help at all please??

is there a way to do a hard reset of sorts? There is nothing I need to save from on, just need to get it working again 😟