The full title of this Microsoft Knowledge Base article is “Windows no longer starts after you install an earlier version of the Windows operating system in a dual-boot configuration”.
After you install an earlier version of the Windows operating system on a Windows 7-based computer in a dual-boot configuration, you may experience one of the following issues:
- If you install an earlier version of the Windows operating system on a Windows 7-based computer, Windows no longer starts. In this case, only the earlier version of the Windows operating system starts.
- If you install an additional instance of Microsoft Windows XP on a computer where Windows XP and Windows 7 are already installed in a dual-boot configuration, you may receive the following error message:
Disk read error has occurred.
These issues occur because earlier versions of the Windows operating system are incompatible with the Windows 7 startup method. Windows 7 uses a Boot Configuration Database (BCD) store. This store contains a boot menu and all the information about operating systems that are installed on the computer. Therefore, a Boot.ini file that is from an earlier version of the Windows operating system cannot be used to start Windows 7.
Refer to the for more information and how to resolve this issue.
Posted in Startup Problems