I’m currently installing Puppy Linux on an old computer, and everything is working fine, the resolution of the boot selections were looking ok, but the moment Puppy Linux boots the GUI, this happens!!! And I tried resizing from the GRUB terminal but it doesn’t work, please help me, thank you!!
Try booting with kernel flag --nomodeset. If it gets you to the desktop, you could find out more about the graphics card and monitor.