virtualbox.org

I have all data, including VirtualBox disks and machines, on a separate partition. I have done a clean install of the OS. I reinstalled VirtualBax and changed preferences for disks and machines to the existing folders. VirtualBox does not recognise any disks already defined. How can I get VB to access the existing stuff?

I assume it doesn't recognize your existing VMs either, not just the disks. The problem is that you forgot about your <home>\VirtualBox.xml file, where all registered VMs and disks are listed. Since it is too late to go back now you will have to recreate all the VMs, I suggest keeping the old VM settings file in notepad++ (or similar) to use as a reference when you do this, since you will need to get all settings exactly as they were before (pay particular attention to MAC address, hard disk controller type, IO APIC setting, and networking mode). When you get to the disk creation step of a new VM, select "Use existing" instead, and point VBox at the appropriate virtual disk file, add it to the registered list and select into the VM.