Yes thankfully I did have a backup. I cloned the harddisk onto an SSD and upgraded that.
I will probably clone the harddisk again onto the SSD and keep it for Win XP, as there are a lot of programmes which I use. I was kind of hoping 'upgrade' meant upgrade, not wipe clean and start again.
Has anyone upgraded Windows 8 Consumer Preview to Windows 8 Pro? Does it keep the installed programmes?