GKLebak

Thanks - I tried your suggestion of holding down Ctrl+Shift while starting - this produced the "Do you want to allow this app to make changes to your device" dialog box. I clicked "Yes" but the program still didn't manage to launch. I should also mention I have performed a complete uninstall and reinstall of R13 (I had to disable my GPU to uninstall and reinstall).

Following the most recent Windows 10 updates I was unpleasantly surprised to discover that both Cinema 4D R13 and its setup software would no longer launch - they just appear briefly in Task Manager for a few seconds then vanish. I discovered that if I went into Windows' Device Manager and disabled my graphics card, this allowed both items of software to launch and run, but this was not really a satisfactory solution. I tried installing an older version of the graphics card driver, but this made no difference, indicating that the problem wasn't with the driver, but with one of the recent Windows updates. However, none of them seem to have anything in them related to graphics. Windows 10 Version 20H2 GPU: Nvidia GT640