Definitely give that environment variable I mentioned in post #6 a shot. You may want to reboot after setting it to make sure it's "live". If you need help setting an environment variable, just ask.
EDIT: Sorry. Just noticed the part where you said my suggestion might be above your tech pay grade. I'll leave some instructions just in case you're ever feeling adventurous.
1) type "env" (without the quotes) in your search box on your taskbar.
2) click the "Edit the system environment variables" link that appears in the right hand column of the popup window.
3) look for the "Environment Variables" button near the bottom of the ensuing dialog and click it.
4) in the top half of the next dialog (User variables), click the "New" button.
5) in the "Variable name" box, type: QSG_RHI_BACKEND
6) in the "Variable value" box, type: "opengl" (without the quotes); and then click the "OK" button.
7) click the OK button on the Environment Variables dialog.
8) and finally click the OK button on the System Properties dialog.
9) reboot to be safe and try running Sigil again.