These instructions to disable or uninstall the pilot version of Microsoft Windows Genuine Advantage Notifications are from the horse's mouth i.e. Microsoft itself.

Note: If you are looking to cleanly remove Windows Genuine Advantage Final version then look here.

Disable WGA Notifications

1. Log on to the computer by using an account that has administrative permissions.
2. Make sure that the WGA Notifications version that exists on the computer is a pilot version. The version format for the pilot version is 1.5.0532.x. In this case, you can uninstall versions 527-532 only. For example, you can uninstall versions that range from 1.5.0527.0 to 1.5.0532.2. To find the WGA Notifications version, follow these steps:
a. Click Start, and then click Control Panel.
b. Double-click Add or Remove Programs, locate and then click Windows XP - Software, then click Windows Genuine Advantage Notifications, and then click Click here for support information.
c. In the Support Info dialog box, verify the version number, and then click Close.
3. Rename the following files by changing the extension to .old:
» Rename %Windir%\system32\WgaLogon.dll to %Windir%\system32\WgaLogon.old
» Rename %Windir%\system32\WgaTray.exe to %Windir%\system32\WgaTray.old
4. Restart the computer.

Manually uninstall WGA Notifications


1. Log on to the computer by using an account that has administrative permissions.
2. Make sure that the WGA Notifications version that exists on the computer is a pilot version. The version format for the pilot version is 1.5.0532.x. In this case, you can uninstall versions 527-532 only. For example, you can uninstall versions that range from 1.5.0527.0 to 1.5.0532.2. To find the WGA Notifications version, follow these steps:
a. Click Start, and then click Control Panel.
b. Double-click Add or Remove Programs, locate and then click Windows XP - Software, then click Windows Genuine Advantage Notifications, and then click Click here for support information.
c. In the Support Info dialog box, verify the version number, and then click Close.
3. Rename the following files by changing the extension to .old:
» Rename %Windir%\system32\WgaLogon.dll to %Windir%\system32\WgaLogon.old
» Rename %Windir%\system32\WgaTray.exe to %Windir%\system32\WgaTray.old
4. Restart the computer.
5. Unregister LegitCheckControl.dll by using
Regsvr32. To do this, follow these steps:
a. Click Start, click Run, type cmd, and then click OK.
b. At the command prompt, type the following, and then press ENTER:
Regsvr32 %Windir%\system32\LegitCheckControl.dll /u
6. Restart the computer.
7. Click Start, click Run, type cmd, and then click OK.
8. At the command prompt, delete the following files by typing the Del command. Press ENTER after you type each command.
» Del %Windir%\system32\wgalogon.old
» Del %Windir%\system32\WgaTray.old
» Del %Windir%\system32\LegitCheckControl.dll
9. At the command prompt, type regedit.
10. Locate and then right-click the following registry subkeys. Click Delete after you locate each subkey.
» HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\WindowsNT\
CurrentVersion\Winlogon\Notify\WgaLogon
» HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows \CurrentVersion\Uninstall\WgaNotify

Source: Microsoft KB