Reregistering Microsoft Office file associations
Had a hardware fault on the laptop and while running through some tests accidentally activated the copy of Office 2007 that came installed with it and it changed all the file associations over. Theoretically this should be easy to change back - locate a Office file, right-click and chose "open with" then locate the excel executable I want to use and set this as the default. Yeah right.
Despite changing the icon and appearing to change it in the registry it still insisted on running the new version.
In the end in took opening up a command prompt changing to the correct Office directory and running each executable with "/unregserver" at the end and then "/regserver" to set them all back to default.