I then discover it's the wrong picture.
Is there any way of replacing the picture with a different file (of the same aspect ratio, and in fact probably the same size to within pixels ... these are all coming out of a complicated make-orchestrated pipeline with perl scripts and gnuplot and ghostscript in it, on a Linux box which doesn't run powerpoint, and being carried across the room many times on a memory stick), keeping the size and position?
At the moment I've been carefully remembering the size and position, deleting the old picture, inserting the new one, and re-entering size and position; by the thirty or fortieth repetition of this, the calm tranquillity instilled in me by infinite turkey over the festive period is really no longer to be seen.
I have spent three days producing this blasted presentation. It's only 20 slides long, but has filled the muscles of my shoulders with stress much more than previous three-day episodes of coding up complicated analyses of the neighbourhoods of metal ligands across the entire protein structure database in C++ managed. I'm not giving it, nor even attending the conference it's being given at!
But it is the weekend now. The Met Office says the entirety of England will be afflicted with violent gales and strong rain, so I won't be able to take my new tripod to photograph ducks at Wicken Fen; I think I will mostly hibernate, though I need to venture out of the house to buy a new microwave. I have five and a half David Attenborough DVDs to watch, and comforting books to read, and there is lots of curriable chicken in the freezer and much curry sauce in the fridge.