Windows 7 VM won't boot after upgrading to Ubuntu 15.10

[qwertyasdf]

I recently upgraded my host from Ubuntu 14.10 to 15.10.

My Windows 7 VM, which worked under Ubuntu 14.10, now will not boot under Ubuntu 15.10. It loads Windows Error Recovery and the two options "Launch Startup Repair (recommended)" and "Start Windows Normally" both attempt to load but then fail shortly after.

Has anyone else experienced this or possibly have a solution?

I've included the VBox.log file in two parts (since it was too large to upload in one file).

[mpack]

I see you are using VirtualBox 4.3.28. Does the problem still occur with a later VBox version?

p.s. Please in future compress your logs rather than break them into several parts.

[mpack]

Looking at the log - it looks like you have an invalid saved state, possibly due to the change of hosts. You should discard this, as saved states are not intended to be portable.

[qwertyasdf]

The option to discard saved state is greyed out; should I remove the VM, upgrade Virtualbox, and then add the VM back in? Or is upgrading for this task unnecessary?

I'm trying to avoid having to set up the Windows environment from scratch and was hoping some installed programs and files would still be there when I restart the VM.