Within days of using this rebuilt tower, the computer started throwing both blue screens with "Critical Process Died" and DOS-like black screens with "hard drive not recognized" and no bootable device".  I ran some recovery options (some of which never fully completed) and that seemed to do the trick for a couple of months.  Earlier this week, the same problems came back and nothing worked to resolve the issues.  The computer kept shutting down.  My 90 day window closed and both Amazon and TekRefurbs refused to make things right.