Enter BIOS/UEFI settings and disable Secure Boot. Secure Boot often prevents Linux-based bootloaders from launching. Also, ensure your USB drive is set as the first boot priority in BIOS.
64-bit Intel or AMD CPU (hence the amd64 designation). Memory: At least 512 MB of RAM. checkn1x-1.0.6-amd64.iso
Because the PC boots directly into Linux, checkra1n has direct access to the USB port, eliminating "USB device not found" errors common in virtual machines. Enter BIOS/UEFI settings and disable Secure Boot