The Microsoft Windows Operating System (OS) is one of the most widely deployed operating systems in the world. Microsoft upgrades the OS every two to four years in order to bring the latest functionality, features, and security upgrades to the end-user. Unfortunately, each new version of Windows does not prove to be compatible or supported by the hardware users attempt to install the upgrade. This can be for a number of reasons from insufficient RAM to not enough available hard drive space resident on the user's computer. A common task that can arise for users who install new Windows OS's is to uninstall Windows. Microsoft does not support an OS feature which allows you to remove Windows that was originally installed on a computer in order to prevent inadvertent deletions.  How to uninstall windows

How to uninstall Windows XP  

Step 1 – Restart the computer in Windows Safe mode by rapidly depressing the “F8” function key during normal computer reboot.

Step 2 – Ensure you log-on to the computer with an account that has administrator privileges. Then, select the “Start” menu followed by “Settings” and “Control Panel.”

Step 3 – Select the “Add or Remove Programs” menu option followed by clicking the “Uninstall Windows XP” menu option under the Windows XP program icon on the subsequent listing of programs.

Step 4 – Select the “Yes” menu button when prompted if you want to conduct a Windows XP Removal.

Step 5 – Restart your computer normally and the previous OS installed before Windows XP will be restored.

How to Uninstall Windows XP from the Command Prompt

Some users may have the need arise to manually uninstall an upgrade to Windows XP from the DOS command prompt if using the Control Panel method fails.

Step 1 – Restart your computer in Windows Safe Mode. After the computer restarts, select the “Start” menu followed by “Run” and enter “CMD” followed by the “Enter” key.

Step 2 – Enter “cd” at the command prompt followed by the “Enter” key. Then, enter “cdwindowssystem32” followed by the “Enter” key.

Step 3 – Enter “osuninst.exe” followed by the “Enter” key.

Step 4 – Choose the subsequent, default menu options to continue with the Windows XP manual removal and reinstall of the previous OS.

How to Uninstall Windows Vista

Before uninstalling Windows Vista, check to make sure that the old version of Windows was backed up to a folder named Windows.old stored on the local or “C” drive of your computer. You can verify this by pressing “Windows” and the “E” keys simultaneously and visually checking for the presence of the folder. If the folder does exist, proceed with the following steps:

Step 1 – Insert the Windows Vista CD/DVD and choose the option to repair your computer when prompted.

Step 2 – Choose the install of Vista on your computer to remove followed by the “Next” button and select the command prompt menu option.

Step 3 – Enter “C:” followed by the “Enter” key. Input “CD” and “Enter.”

Step 4 – Input “ren Windows Windows.Vista” and “Enter.”

Step 5 – Enter “ren “Program Files.Vista” and “Enter” followed by “rd Documents and Settings” and “Enter.”

Step 6 – Input “Xcopy /s /h c:windows.old*.* c:” and “Enter” and agree to overwrite files if prompted.

Step 7 – Type “D:bootbootsec /nt52 c:” but ensure the letter for the drive matches that of the installation CD drive.

Step 8 – Enter “c,” “enter,” “cd,” “enter,” and “attrib boot.ini.saved -s -h -r” followed by the enter key.

Step 9 – Input “Exit” and click the “Restart” menu button in the System Recovery Console menu options to complete remove of Windows Vista.

How to Uninstall Windows 7

Many users who upgraded to Windows 7 did not necessarily have the recommended amount of RAM installed on their computer to support running Windows Vista. As a result, performance of some versions of Windows 7 can be degraded if the computer hardware does not support the minimum specifications of the OS. In order to remove an upgrade to Windows 7, conduct the following steps:

Step 1 – Select the “Start” and “Computer” buttons.

Step 2 – Select the “Details” option on the “View” menu. Then, double-click the “Local Disk” which is normally labeled “C:” to see if there is a folder named “Windows.old” on the “C” or “Local” Drive. If the folder exists, you will be able to remove Windows 7 and revert to the previous OS.

Step 3 – Insert the Windows 7 install disk in the CD/DVD drive and restart your computer. Enter a key when prompted to restart from the install disk.

Step 4 – Choose the “Time, language, currency, and keyboard input method” followed by the “Next” button.

Step 5 – Select the “Repair Your Computer” menu option and then choose the version of Windows 7 installed on your computer followed by the “Next” menu button.

Step 6 – Click the “Command Prompt” option in the System Recovery Options Window.

Step 7 – Enter “C:” followed by the “Enter” button. Then input, “Md Win7” and “Enter.”

Step 8 – Input “Move “Program Files” “Win7Program Files” and “Enter.”

Step 9 – Enter “Move Users Win7Users” and “Enter.” Then, input “Attrib -h -s -r ProgramData”

Step 10 – Type “Move Program Data Win7ProgramData” and “Enter” followed by “Rd “Documents and Settings” and “Enter.”

Step 11 – Enter the following commands at the DOS prompt followed by the “Enter” key to reinstall the old operating system:

move /y c:Windows.oldWindows c: 
move /y "c:Windows.oldProgram Files" c: 
move /y c:Windows.oldProgramData c: 
move /y c:Windows.oldUsers c: 
move /y "c:Windows.oldDocuments and Settings" c:

Step 12 – Restore the appropriate boot sector for the legacy Windows version that was previously installed. For Windows XP, 200, or Windows Server 2003 enter the following command:

D:bootbootsect /nt52 c:

For Windows Vista enter this command:

D:bootbootsect /nt60 c:

Step 13 – Restore the Boot.ini file if restoring Windows to Windows XP or Windows 2000 by entering the following command followed by the “Enter” key:

Attrib –h –s –r boot.ini.saved
Copy boot.ini.saved boot.ini

Step 14 – Restart your computer and Windows 7 will be removed.