How did you partition the disk? grub4dos installer complains about bad partition table: Go to disk management. Backup data if you have such on the USB disk. Delete all partitions. Create new ones. Set first one active. Using safely remove hardware icon disconnect the disk. Replug it and try the program again. I partitioned the disk by the same program "grup4dos" but when I did what is you said now, it work correctly thank you very much