For a Microsoft Office 2003 version of this article, see 836178
When you open a Microsoft Office program, you see the user information screen, which prompts you for your user name, initials, organization, and product key. After you type all of the requested information, you receive the following error message:
Please enter a valid product key to use this product - setup has detected that the product key is missing or invalid. You will find this 25-character key on your Certificate of Authenticity or the yellow sticker on the back of the case.
This problem occurs when there is more than one installation of Microsoft Office or an Office program on your computer, and the installations are conflicting.
To resolve this problem, remove the duplicate program (for example, Microsoft Word, Microsoft Excel, or Microsoft Office XP Small Business Edition), and then install Office or the Office program again.
This issue may occur when another Office suite (such as Standard, Professional, or Premium) or an Office standalone program (such as Word, Excel, Microsoft PowerPoint, or Microsoft Publisher) is installed on the computer before you install Office XP or Office 2000.
For example, some original equipment manufacturers (OEMs) sell computers with Microsoft Works Suite 2002 already installed. (Microsoft Works Suite includes Word.) If you install Office XP, the earlier installation of Word is not replaced, because the two installations are the same version. Therefore, when you open Word, you are prompted for the product key.