After another Startup Repair attempt it seemed to fix something and now I can boot. Checking the Event Viewer shows a lot of errors that I should probably be concerned about, such as:
The file system structure on the disk is corrupt and unusable. Please run the chkdsk utility on the volume
and there's plenty more errors about this driver failing to load:
The AODDriver4.1 service failed to start due to the following error: The system cannot find the file specified.
So, I'll look into that and probably run chkdsk /r. Maybe it's time to buy a new hard drive.
I also went ahead and did
this. Hopefully that stops the errors.