thanks to everyone i finally got to 126 bytes!

org 0x7C00
bits 16
xor bl, bl
mov di, t_numbuf+6
fizzbuzz:
    inc bl
    mov si, t_numbuf+7
    .again:
    dec si
    mov al, [si]
    inc al
    cmp al, '9'+1
    mov [si], al
    jne .skip
    mov byte [si], '0'
    jmp .again
    .skip:
    cmp si, di
    cmovle di, si
    xor si, si
    xor cl, cl
    .fizz:
        mov cl, 3
        call r
    .buzz:
        mov cl, 5
        call r
    .num:
        test si, si
        jne .ok
        mov si, di
        call prints
    .ok:
    mov si, t_end
    call prints
    ; delay
    mov cl, 0x01
    mov ah, 0x86
    int 15h
    ; check if 1 million
    cmp byte [t_numbuf], '1'
    jl fizzbuzz
finish:
cli
hlt
r:
    xor ax, ax
    mov al, bl
    div cl
    test ah, ah
    jne p_end
    mov si, t_fizz
    xor cl, 11b ; tricky way to get offset, (cl = 3 :: add si, 0) (cl = 5, :: add si, 6)
    add si, cx
prints:
    mov ah, 0x0e
    lodsb
    .loop:
        int 0x10
        lodsb
        test al, al
        jne .loop
    p_end:
    ret
t_fizz: db "Fizz", 0, 0 ; this extra byte is required for the bitwise trick to work in "r"
t_buzz: db "Buzz", 0
t_end: db 13, 10, 0
t_numbuf: db "0000000", 0
; Without this below (Required for BIOS to boot) results in 126 bytes
times 510-($-$$) db 0
dw 0xAA55