Dual system installation and startup principle

98/ME and 2000/XP dual system installation and startup principle

Let me talk about MBR (master boot sector) and system boot sector:

The main boot sector is located at the head of the hard disk and is responsible for searching the partition that the hard disk can boot. For DOS, it is generated by Fdisk; and the system boot sector is located at the head of each partition to boot the partition. The corresponding operating system, which is responsible for the sys command.

Secondly, the system startup:

In general, Win98 startup is handled by 5 files: io.sys, msdos.sys, command.com, autoexec.bat And config.sys.

The startup of Win2000 and WinXP is handled by two files, Ntldr and Ntdetect.

Win98 and Win2000/WinXP dual system startup is more complicated, it is booted by OS Loaer, the user can choose which system to boot, if the user chooses to start Win2000/WinXP, then load Ntldr and Ntdetect Two files are booted to Win2000/WinXP; if the user chooses to start Win98, then the Bootsect.dos file is loaded. The Bootsect.dos file is actually the image of the Win98 boot sector.

By the way, there are two files, Ntldr and Ntdetect, in Win2000 and WinXP, but they are different. If you lack these two files in your dual system, you can install the disk from Win2000 or WinXP. Copy the I386 directory. If it is Win2000, you can use Win2000 or WinXP; if it is WinXP, you must use WinXP CD, the two files in Win2000 disk can not boot WinXP, this installation in Win2000 and WinXP In the multi-system inside, the performance is particularly obvious. For example, after you reinstall Win2000, you can't start WinXP. The reason is that you use Win2000 Ntldr and Ntdetec files to cover WinXP's Ntldr and Ntdetec files. So be sure to pay attention!

Let's talk about Windows' multiple operating system boot management tool: OS Loader. Each multi-OS boot management tool is different, such as BootMagic and System Commander are resident in MBR; OS Loader

is resident in the system boot sector; and Linux is more The system boot tool LILO or GRUB can be located either in the MBR or in the system boot sector.

The above is some theoretical knowledge. Since they are all clear, let's go into the theoretical analysis stage and see if the formatted C drive reinstalls Win98. Why can't it be dual booted?

Actually, the reason is very Simple, when you reinstall Win98 on the C drive, your C drive has four files missing: Ntldr, Ntdetec, Bootsect.dos and boot.ini (multi-system boot configuration file). However, only backup these four files before reloading, and then copy them back after reloading, it is also impossible to achieve dual boot! The reason is that the system boot sector of your C drive has been overwritten by Win98: it changed the previous system boot sector controlled by OS Loader into the Win98 system boot sector, so even though you copied back the four File, because the boot sector still does not return to dual boot, so you still can not achieve dual boot.

Knowing the reason, it is only after the solution has the ideas and goals. That is to find a way to restore the system boot sector. There are several methods,

Method 1:

You can back up the system boot sector before reinstalling Win98, you need to use the DEBUG command!

The backup command is:

a:>debug

-L 100 2 0 1

-na:OSLoader.REC

-rcx

CX:0000

:200

-rbx

BX:0000

:0

-w

-q

The OSLoader.REC file generated on the floppy disk is the backup of the OS Loader boot sector. If you accidentally delete the Bootsect.dos file, you can use a similar method. To generate the file, simply change the name of the saved file in the third line to Bootsect.dos.

As long as the OSLoader.REC file generated above is rewritten as the hard disk boot sector, the OS Loader boot function can be restored. The command is:

A:>debug

-Na: Bootsect.dos

-L

-w100 2 0 1

-q

After the OS Lode menu is repaired, if the C drive lacks the Bootsect.dos file, you can copy the generated Bootsect.dos file to the C drive (note: Bootsect.dos file generated on different machines) Can not be universal).

Method 2:

Use the Win2000 or WinXP fault console to recover the boot sector:

To enter the faulty console, type:

Fixboot c :

Exit

Restart your computer.

Of course, both methods are successful in retrieving the dual-boot function on the premise of backing up and restoring the above four files in advance. If you do not back up these files beforehand, it is more troublesome. The simple method is to use the Win2000 or WinXP installation disk repair method, which is the fake installation method; the troublesome way is to copy the Ntldr and Ntdetect files from the Win2000 and WinXP installation disk, using the DEBUG command. Generate Bootsect.dos file, then use Win2000 or WinXP installation disk to enter the faulty console and generate Boot.ini file. (Of course, if the syntax of the file is very familiar, just like my master can also use the note under Win98. I wrote a Boot.ini file according to the configuration of the machine, and then repair the boot sector in the faulty console, restart, and you're done!