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Multi-booting Operating Systems

August 28, 2004

How to install Win98 and Win XP on the same machine?

If you have installed Win XP first and then try to install Win98 next, it won’t work, because Win98 wants to be on the C: drive by default.

The easy way is to install Win98 on C: drive and then install Win XP on D: drive. Win XP provides the NT Boot Loader to boot your chosen OS during system startup.

During installation of Win XP, the file "ntldr" is copied to the root directory of the active partition and the installation routine scans the computer for another known Microsoft OS.

A boot.ini file is created, which ntldr will read at each boot. Boot.ini will be configured with two entries, one for Win98 on C: and the other for Win XP on D:

The XP-Setup routine also copies the existing Win98 partition boot sector into a file (bootsect.dos) and replaces the partition boot sector with a XP version.


Basic concept of installing multiple OS on the same PC

1)      Install first OS on the first partition

2)      Use hard disk utility to hide the first partition

3)      Install second OS on the next partition

4)      Install a boot manager

By switching the hidden/active status of each partition, one partition or the other can be booted while the other is hidden and dormant. Only one partition can be marked “active”.

A boot manager can be use to switch the hidden/active flag. With boot manager, OS are kept independent as the boot manager is loaded before the OS. Installing a third-party boot manager involves the altering of the MBR, and this could be unsafe.

The booted partition is designated "active". The boot process starts by executing code in the first sector of the disk - the MBR. The MBR looks over the partition table to find the "active boot partition” and the boot process continues through that partition.

Non-booted partitions may optionally be set "hidden" so they can't be interfered with by the booted partition.

So when you boot 98 it will be designated C: and the XP partition will be hidden, and when you boot XP it will be C: and the 98 partition is hidden.

Removing the boot manager is as simple as replacing the MBR again with a standard version. “fdisk/mbr” in DOS should do the trick.


Steps to install a second OS, Win 98 on an existing Win XP system

Prepare the hard disk

  1. Boot the Win XP

  2. Remove all temp files, C:\temp  , C:\Windows\temp, Temporary Internet files

  3. Scandisk (Optional, ntfsresize should take care of that)

  4. De-fragment disk (Optional, ntfsresize should take care of that)

  5. Shutdown

Installing a second OS need to re-partition the hard drive. It is safer to backup the existing system.

  1. Attach a hard disk to the secondary IDE port
    (Note: Hard disk Must be BIG enough to store image)

  2. Boot Ghost Boot CD-ROM

  3. Choose "Disk to image", store image file to the backup hard disk

Use ntfsresize to shrink the existing hard disk

  1. Boot Knoppix Live CD
  2. At command prompt, run ntfsresize
  3. ntfsresize --info /dev/hda1
  4. ntfsresize --no-action --size 10000M /dev/hda1
  5. ntfsresize --size 10000M /dev/hda1
  6. sfdisk -d /dev/hda > hda.pt
  7. dd if=/dev/hda of=hda.mbr bs=512 count=1
  8. run fdisk to delete and recreate primary partition to a size larger than the resized ntfs volume, eg 10200, set type to 7, make it active

    #fdisk /dev/hda
    Command (m for help): p
    Command (m for help): d
    Command (m for help): n
    Partition number (1-4): 1
    First cylinder (1-2480, default 1): 1
    Last cylinder or +size or +sizeM or +sizeK (1-2480, default 2480): +11000M
    Command (m for help): t
    Hex code (type L to list codes): 7
    Command (m for help): a
    Command (m for help): p
    Command (m for help): w
  9. ntfsresize --info --force /dev/hda1

Boot Win XP to ensure it is okay.

Next, boot win98 setup CD.

Asked if want to remove unknown system files? NO!!!

At some point of time, after formatting the C: drive, there may be an error.

Possible Error

After Win98 setup formatted the hard disk (the unallocated space), it will complain that the format is not complete due to some kind of error, and now the file system is not compatible.

This is what you can do:

1) Boot a DOS floppy and format the C: drive. The C: drive (FAT32) is created during the Win98 setup.

2) Copy the cab files from Win98 directory of the setup CD to the C: drive

3)  Run Setup from C: drive


Warning that Win98 cannot see WinNT partition. It is OK.

Win98 create its own partition, format it, install itself

After install finished, Win98 boots from the hard disk.

Install Smart Boot Manager, SBM from DOS


David Lee's comment dated Friday, June 10, 2005 1:32 PM

Re: Multi-booting Operating Systems,August 28,
2004 article.

I suggest that you parition the HD first for two
OS. Making the mistake of using the same "Program
Files" directory on the same HD "C:\\Program
Files" will result in confusion over which
applications are win9x and which are NT.

If you make the C: just for win 9x and then use D:
for NT-XP your prevent removal headachs when you
try to uninstall applications with shared DLLS.


Last Update: 03 March 2004