VM doesn't start after host hard shut down

[Nogfurt]

I have a VM running on a desktop that had the power cable pulled out forcefully. After that, I haven't been able to start the VM and get the message

VBoxManage: error: Details: code NS_ERROR_FAILURE (0x80004005), component Machine, interface IMachine, callee

Would the "reset" option fix it? It is a long running VM and it has days and days of work which I cannot lose. What exactly does "reset" do? Thanks!

[Perryg]

Check the size of the *.vbox file or if it even exists. Now compare it to the *.vbox-prev and see if there is a difference.
If so replace the *.vbox file with the *.vbox-prev

[Nogfurt]

Thanks for the response. They both seem to be around 47K. I just realized I tried starting a different VM and it did not startup either, I'm getting the same error. Could there be something else that is going wrong?

[socratis]

I have a VM running on a desktop that had the power cable pulled out forcefully

I would start with the desktop and make sure that there was no HD corruption when the power was lost. After that, an uninstallation and re-installation of VBox, and finally start worry about my VMs.