Convert Hyper-V dynamic disk to fixed size

By default when you create a new VM in Hyper-V - and a create a virtual disk at the same time - it creates a dynamic disk (i.e. it expands to the specified size as required). This is not usually a recommended option for production environments, albeit the official advice tends to change with the weather, so you should convert the dynamic disk to a fixed disk using Hyper-V Manager as per the excellent instructions provided by Carl Gray (aka the OxfordSBSGuy)