windows xp - Installing XP from the same partition

I have a rather unusual question.

I have a computer with one disk with valuable data and no removable media. It is not possible to create a new partition on said disk.

Basically what needs to be achieved then is to install the Windows XP operating system from disk0part0\INSTALL (which is an install CD copied to that subdir) to disk0part0\WINDOWS without formatting the disk itself.

Is such a thing possible?

Answer

I've just tried it in a virtual machine and it seems to be possible.

This procedure isn't recommended and may result in data loss. You're performing in on your own risk. Make complete backup first.

Obviously visible side effects include:

• Non-standard name of Windows directory (eg. C:\WINDOWS2 instead of C:\WINDOWS)


• Non-standard names of user directories (eg. C:\Documents and Settings\All Users.WINDOWS2, C:\Documents and Settings\gronostaj.COMPUTERNAME-RANDOMSTRING

Some serious issues may appear later when using system installed in such way.

I'm assuming entire Windows XP installation disk is copied to C:\INSTALL and it's the only available partition (thus also the partition that you're reinstalling to).

This is the method based on installer provided by Microsoft.

1. 
   

   Run C:\INSTALL\Setup.exe, the official Windows-based installer for XP. Choose to perform clean install. Accept the license, enter serial key (the same one that is currently used is allowed), check settings and correct anything you don't like. Reboot.

   
   


2. 
   

   You will be asked which environment you'd like to boot: your old XP instance or Windows Installer. Choose Installer.

   
   


3. 
   

   Wait until the installer loads. Press Enter, accept license. Choose your only partition. Installer will warn you that Windows is already installed there. Agree to install anyway. You will be asked for new Windows folder name. You have to choose something different than \WINDOWS or things will break. I tried with \WINDOWS2. The rest of the installation process is identical as when installing Windows from a disk to a clean drive.

   
   


4. 
   

   When the installation completes, you'll have two Windows XP entries in the boot menu. The first one is the new instance. Boot it and delete any leftovers from the old instance. (described below).

   
   

If you don't like the official way for whatever reason, here's alternative one. It's relying on some potentially unsafe hacks, so be careful.

1. 
   

   Open Disk Management console (right-click My Computer, choose Manage computer and Disk management in the left panel). Right-click C:\ drive and choose to change drive letters.

   
   


2. 
   

   In the new window choose to mount the drive in a directory. Create an empty directory on C:\ drive, call it mount and choose it. Now you should have two paths visible for that drive: C:\ and C:\mount.

   
   


3. 
   

   Open the command prompt. Issue the following command:

   
   

   subst W: C:\mount
   

   
   

   It will mount C:\mount directory as a W: drive. Remember that C:\mount is already a mount point for C:\, so we will effectively create an alias for C:\. This way we will circumvent two limitations: WinNTSetup (which we will use later) won't let you install to C:\ while running Windows from C:\ and Windows won't let you create a drive letter alias for the system drive.

   
   


4. 
   

   Run WinNTSetup. Configure following options:

   
   
   
   
   • Installation files directory: C:\INSTALL
   
   
   • Boot drive: C:\
   
   
   • Installation drive: W:\
   
   
   • Windows directory name: enabled, C:\WINDOWS2 ← this one is important!
   
   
   
   

   Click Setup, wait until WinNTSetup completes. Reboot.

   
   


5. 
   

   Reboot to Windows installer. The first installation phase will run in unattended mode. It will copy required files and reboot to second phase which goes just like in the official method. Final effect should be identical. Remove any leftovers.

   
   

Before removing any leftovers you should copy your files from the old profile to the new one. This includes My Documents and other similar folders.

Open C:\ in Windows Explorer, accept the system drive warning. Delete following folders:

• C:\WINDOWS - the old Windows installation directory


• C:\Documents and Settings\All Users - the shared user direcotry from the old instance


• C:\Documents and Settings\{YourOldUsername} - your user directory from the old instance

You will be asked if you really want to delete system files, read-only files etc. Always click Yes to all.