Keynote to Powerpoint and CMYK

I have a number of presentations which I give in different locations where I have to use other institutions' hardware setups. Needless to say, they are all focussed on Windoze and expect me to use a PC. Usually I can connect my Mac into their VGA projector but occasionally I have to convert my keynote presentation to Powerpoint to run on the provided PC.

Quite often my presentation will include CMYK files which project quite normally in Keynote, but when converted to Powerpoint only one channel is visible. Is there a way
a) for Powerpoint to see the full four channels?

or b) for keynote to convert the images contained within it to RGB?

or c) do I have to convert each CMYK image individually in Photoshop before importing them into Keynote?

On a different note, sometimes when I connect my mac to a VGA cable my Mac screen scrambles. Anyone else come across this and if so is the mac faulty (MacBook Air 1st generation) or the projector/VGA cable at fault?

Thanks