Ran across a problem today where a legit Office 2003 got flagged as being not legitimate, displaying a nag screen each time an Office application got started. The Office Genuine Advantage update (short: OGA) is an update installed with Microsoft Update, similar to the Windows Genuine Advantage update (short: OWA). While Microsoft flags the update as not uninstallable, there are ways to get rid of the update anyway.

Uninstall the update

Uninstalling the update is your best bet, and can be done from a (elevated) command prompt.

1. Be sure all Office applications are closed.
2. Open a Command prompt (cmd.exe).
3. Type in: msiexec /X {B2544A03-10D0-4E5E-BA69-0362FFC20D18}
   This will invoke Windows Installer with the command to uninstall a certain update: KB949810.
4. Wait for it, and done.

Notice

Note that you need to hide the update KB949810 from Microsoft Update, or it will be installed again.

Disable the OGA notification add-in

An alternative to uninstalling OGA is disabling it in Office. This can be done quickly using the registry editor.

1. Be sure all Office applications are closed.
2. Start up regedit, and search for the string OGAAddin.connect.
   You'll come across a few occurences in HKEY_CLASSES, leave those alone.
3. In HKEY_LOCAL_MACHINES, there will be more occurances, along with a value called Load behaviour. By default it will be set to 3. Set it to 0 to disable the loading of the add-in.
   Repeat this for all Office applications (Word, Excel, Powerpoint, etc.).

Manually erasing OGA files

The least preferred method is actually deleting the files of OGA.

1. Be sure all Office applications are closed. If you get file in use messages, there's still something Office-related running.
2. Depending on your version of Windows being 32-bit or 64-bit, navigate to either:
   C:\Windows\System32 (32-bit) or
   C:\Windows\SysWow64 (64-bit).
3. Find and delete the files: OGAVerify.exe and OGAAddin.dll.

Avoid using other third party tools such as hacks or cracks. They are unnecessary to solve this problem and usually only compromise your system's security.