Problem

In
order to install or reinstall Microsoft Windows you must have access to a
Product Key for that version of the operating system. The product key can
typically be found on a yellow sticker on the CD case of the installation CD,
or on a small Microsoft sticker on the outside of the PC’s case (if the OS came
preinstalled on the machine). If you no longer have access to the product key
then you will effectively “lose” a Windows license if you ever have
to reinstall the operating system.

Solution

There
are several methods you can use to uncover a lost product key for a version of
Windows that you currently have installed.

For
older versions of Windows you can extract the product key from the Windows
Registry. Click Start | Run and then type regedit and click OK.

For
Windows 95 and Windows 98, browse to this key:

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\ProductID

For
Windows NT 4.0, browse to this key:

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows NT\CurrentVersion\ProductID

Alternatively,
there are also some free scripts and freeware software programs that can help
you:

  • Magical
    Jelly Bean Keyfinder:     This is probably the best tool
    for this task. In addition to finding and identifying product keys for
    Windows 95/98/ME/NT/2000/XP, it can also uncover product keys for
    installed versions of Microsoft Office.
  • Windows
    Key Finders:
    This is actually a group of tools that can be used for unearthing product
    keys for different versions of Windows.
  • Belarc Advisor: This free utility builds a detailed profile of
    your installed software and hardware. (As suggested in the discussion
    thread by ShadyHouse).

Whichever
method you use, make sure you write down the product key and put it in a safe
place for future reference.