Just updated to Office 2013 and opened a spreadsheet that I have
developed only to find it now ran like dog. You could literally watch
the movement when you changed cells. Apparently this version has
animation built in.

There is a fix but it's not intuitive.

It involves going to the Ease of Access centre in Control panel.
You select use the computer without a display and then tick the checkbox
turn off unnecessary animation. Voila your spreadsheet responds quickly
again.

Why Microsoft WHY???