If old software you want to install does need unsigned drivers, you'll have to use a special boot option to install them. Related: What Is UEFI, and How Is It Different from BIOS? You should only install unsigned drivers if you know they're safe and have a good reason to do so. Enforcing signed drivers helps improve security and stability, protecting your system from drivers that are malicious or simply unstable.
The exception to this is that 32-bit versions of Windows 10 running on a newer PC with UEFI (instead of regular BIOS) often do require signed drivers. 32-bit versions of Windows 10 normally don't require signed drivers. The 64-bit version of Windows 10 uses driver signature enforcement and requires all drivers have a valid signature before they can be installed.
Install Unsigned Drivers or 32-bit Drivers
