1. Download BurnOut.exe utility.
2. For Rhino 9:

   BurnOut.exe /uninstall {9FD57E3C-6A27-4151-A408-E9C7487CBFC4}

3. For Rhino 8:

   BurnOut.exe /uninstall {851D74A0-D029-4AC7-9CBE-E50455C24237}

4. For Rhino 7:

   BurnOut.exe /uninstall {F7D93B42-988E-462F-8D0B-4CFE68701F6D}

5. For Rhino 6:

   BurnOut.exe /uninstall {730997CF-7DB0-427E-A829-16BCCBCF569D}

This will find and uninstall any version of Rhino on the computer. Note that uninstall doesn't remove per-user files that were created during or after installation.