Cannot Install Update

Whenever I check for an update via the check for updates option on media player 10 I get the following message:

"A more recent version of Windows Media Player is already installed on your computer. Setup cannot continue ".


However, whenever I try to install update KB926251 which is meant to prevent the above message I get this message:

"Setup has detected that the service pack version of the system is newer than the update you are applying. There is no need to install this update ".

In contrast I have run the Belarc Advisor on my computer and it says that KB926251 is missing and should be installed.