20Gig file blocking the hard disk

A neighbour has a problem.  A 20Gig file in her Vitus Defs file has completely blocked her computer.  I only has a small hard disk.

 

I have tried deleting the file. I have tried uninstalling symantec/Norton.  I have tried re-naming the file for deletion. I have opened the machine in safe mode and tried to change the settings to remove the read only status.  Nothing shifts it.  I have read that faulty virus defs have caused problems with large files but probably thos machines had enough disk capacity to allow them to carry on functioning and the problem probably fixed itself with the next update. In this case the machine is just too blocked.  Any suggestions?

 

Idea