Click here for Windows XP

Click here for DOS

For Windows 98 and Windows ME

Assuming your system is still in operational condition, go to www.dougknox.com, click on Utilities, at left, then look for "Find Product (CD) Key". That's a VBS script that will find the Product Key for you or click Software or the navigation bar above and download the latest version of GEOSoft RegInfo from the applications page.

The W98 Product Key is generally found on the Windows user manual, the certificate of authenticity, a sticker on the PC, or the sleeve or jewel case the Windows' CD came in. The key also might be available from the system.

If the system is working in either safe or normal modC:
Open regedit.exe to this key and navigate to:
HKEY_LOCAL_MACHINE\Software\Microsoft\Windows\CurrentVersion
Look in the right-hand pane for the value "Productkey" (all one word). The value data is the number required to install Windows.

The following two suggestions assume that you have installed Windows to the default drive and folder.  If you have done otherwise, you will have to adjust the path.

If the system is not working, but Windows is still installed, start the computer with a floppy startup disk.
At the A: prompt, type:
%windir%\command\find /n "ProductKey" %windir%\system.dat
(NotC: ProductKey must be typed in upper and lower case letters exactly as shown and there is a space after: "find" after: "/n" and after "ProductKey".  You could also download pk.bat from this page SoftFixes.htm. Copy it to your Windows startup disk and at the command prompt type:
pk

If that does not work, start the computer with a floppy startup disk.
At the A: prompt, type:
%windir%\command\find /n "ProductKey" %windir%\system.1st
(NotC: ProductKey must be typed in upper and lower case letters exactly as shown and there is a space after: "find" after: "/n" and after "ProductKey"

You could also download a copy of RegInfo.
RegInfo will recover the key for you.  Also see Hardware > System Info in the menu.

For Windows XP

The Windows 25-character Product Key (required to perform the installation) is stored on the CD packaging on a bright orange sticker that says "Do not lose this number." If it was an OEM (factory installed) license, it's stored on a label that the PC manufacturer affixed to the exterior of the PC case (almost any place on the case), or on the bottom of a laptop.

To recover a lost Product Key:

*If your system still runs*, you should be able to use AIDA32 Enterprise from:
http://www.aida32.hu/aida32.php
or ViewKeyXP from:
http://www.webtree.ca/windowsxp/repair_xp.htm
to find the Product Key. (If you have a factory-installed OEM license, and haven't since reinstalled the OS, the revealed Product Key is probably of the drive image used at the factory and *not your specific* Product Key; therefore, it probably cannot be, and *definitely should not be* used for a re-installation.)

If it was a retail license and you have proof of purchase see this link:
How to Replace Lost, Broken, or Missing Microsoft Software or Hardware [326246]
http://support.microsoft.com/default.aspx?scid=KB;en-us;326246

If it was an OEM license, you should contact whomever sold you the OS; although very few manufacturers/vendors keep records of the Product Keys they have sold, it's worth a try before you have to buy a new license.

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For DOS

This will only work on a Windows 9x systems as far as I know

To recover a lost Product Key:

Start the computer with a floppy startup disk.
At the A: prompt, type:
%windir%\command\find /n "ProductKey" %windir%\system.1st
(NotC: ProductKey must be typed in upper and lower case letters exactly as shown and there is a space after: "find" after: "/n" and after "ProductKey"

Just to make it easy you can download a pre-made batch file from this site. Just use the menu and navigate to Software > Solutions.  It's number 3 on the list.

Save the file to a floppy disk or place it in the C:\ root directory.

To use it, start the computer with a floppy startup disk.

• If you saved it to a floppy disk
  • Boot the computer using a Windows Startup disk.
  • After the system is started you should see an A:\> prompt
  • At the A:\> prompt remove the startup disk, insert the floppy with the batch file and type pk then press Enter
  • It should recover the number as long as the Windows files are intact
  • Write the number down where you will be able to find it.

 

• If you saved it to C:\
  • Boot the computer using a Windows Startup disk.
  • After the system is started you should see an A:\> prompt
  • At the A:\> prompt, type cd c: (don't miss the space between cd and c:)
  • At the C:\> prompt type pk then press Enter
  • It should recover the number as long as the Windows files are intact
  • Write the number down where you will be able to find it.