How to restore a computer to a previous Windows installation in a dual/multi boot situation

Action
A clean installation with NO format was performed on a partition containing a legacy OS (Windows XP).

Result
The legacy OS is no longer bootable.
Cause
Bootable installations of Windows Vista and Windows XP cannot simultaneously exist on the same partition. When Windows Vista is cleanly installed, with no format, on a partition that already contains an existing Windows XP installation, The following Folders from the legacy OS are moved to a Windows.old folder:

Windows>Program Files>Documents and Settings

Resolution
The following steps provide an option to revert back to the legacy OS if the Windows Vista installation was done in error:

1. Boot into the Windows Recover Environment (WinRE) Command Prompt using the Windows Vista installation DVD.
2. Identify the partition in which Windows Vista was installed (this partition would contain the Windows.old folder).
3. Type the following commands where Z: is the partition that was identified in Step 2.

Z:cd\ren Windows Windows.vista>ren “Program Files” “Program Files.vista”>rd “Documents and Settings”
xcopy Z:\WINDOWS.OLD\*.* Z:\ /s /h

The preceding commands rename the installed Windows Vista folders and removed the Documents and Settings junction. The Windows XP folders located in the Windows.old folder are then copied back to the root of the drive.

4. Repairing the boot configuration of the legacy OS can depend on what other operating systems exist on the computer. Read these carefully and choose the scenario that describes the computer and type the commands where C: is the active partition (the partition that contains the boot files):

Note: When clean installing Vista over a single Windows XP installation, the boot entry for XP is left in the boot.ini, but the boot.ini is renamed. Bootsect /nt52 not only makes NTLDR the default boot loader but also renames the boot.ini.saved back to boot.ini. An upgrade to Vista, removes the XP boot entry from the boot.ini if multiple XP entries exist.

A) If no other installation of Windows XP exists on the computer but another installation of Vista does:

C: cd\bcdedit /delete {id} (Note: Where {id} is the identifier of the Vista OS that was installed over Windows XP)bcdedit /create {ntldr} /d "Earlier Version of Windows"
bcdedit /set {ntldr} device partition=c:
bcdedit /set {ntldr} path \ntldr
bcdedit /displayorder {ntldr} /addlast
attrib -s -h -r boot.ini.saved
ren boot.ini.saved boot.ini
notepad boot.ini

Update the boot.ini if needed to include the installation of Windows XP you just reverted back to.

B) If no other installations of Vista exist on the computer:
D:\boot\bootsect.exe /nt52 all (Where D: is the DVD ROM drive containing the Windows Vista DVD)

C) If another installation of Vista AND XP exist on the computer:

C: cd\
bcdedit /delete {id} (Note: Where {id} is the identifier of the Vista OS that was installed over Windows XP)
attrib -s -h -r boot.ini
notepad boot.ini

Update the boot.ini if needed to include the installation of Windows XP you just reverted back to.

NOTE - This is a SAMPLE boot.ini entry:

[boot loader]

timeout=30

default=multi(0)disk(0)rdisk(1)partition(2)\WINDOWS

[operating systems]

multi(0)disk(0)rdisk(1)partition(2)\WINDOWS="Microsoft Windows XP Revert" /fastdetect /NoExecute=OptIn