Recently I get an old laptop for testings. It's BIOS is AMI 1.02C. In BIOS settings it shows option to boot from "Removable Dev.", but somewhy it doesn't work and I use plop boot manager to boot from USB(I tried to boot ubuntu from usb, it booted only with plop boot manager).
I would like to try to boot my operating system, but it doesn't boots. I have tried to copy bootloader using cygwin with "dd bs=512 count=1 if=build/tmpcdcontent/boot/stage1 of=/cygdrive/h/boot/stage1 conv=notrunc", "dd bs=512 seek=1 if=build/tmpcdcontent/boot/stage2 of=/cygdrive/h/boot/stage2 conv=notrunc" and copied kernel.bin file manually. When I select USB from plop boot manager, I get "Reboot or Select proper Boot device", after clicking enter I get isolinux error.
USB is 124MB FAT. Sorry, I'm new in os development and I would like to learn, but my English isn't very well to understand various tutorials.
So any ideas how can I boot it

Thanks, have a nice day.
P.S. os is using GRUB bootloader.