boot.asm

[BITS 16]
[ORG 0x7c00]

start:
    xor ax,ax   
    mov ds,ax
    mov es,ax  
    mov ss,ax
    mov sp,0x7c00

TestDiskExtension:
    mov [DriveId],dl
    mov ah,0x41
    mov bx,0x55aa
    int 0x13
    jc NotSupport
    cmp bx,0xaa55
    jne NotSupport

LoadLoader:
    mov si,ReadPacket
    mov word[si],0x10
    mov word[si+2],5
    mov word[si+4],0x7e00
    mov word[si+6],0
    mov dword[si+8],1
    mov dword[si+0xc],0
    mov dl,[DriveId]
    mov ah,0x42
    int 0x13
    jc  ReadError

    mov dl,[DriveId]
    jmp 0x7e00 

ReadError:
NotSupport:
    mov ah,0x13
    mov al,1
    mov bx,0xa
    xor dx,dx
    mov bp,Message
    mov cx,MessageLen 
    int 0x10

End:
    hlt    
    jmp End
    
DriveId:    db 0
Message:    db "We have an error in boot process"
MessageLen: equ $-Message
ReadPacket: times 16 db 0

times (0x1be-($-$$)) db 0

    db 80h
    db 0,2,0
    db 0f0h
    db 0ffh,0ffh,0ffh
    dd 1
    dd (20*16*63-1)
	
    times (16*3) db 0

    db 0x55
    db 0xaa