Account Problem in Mac Apple Store (not my account !)

I want to download Mavericks but Mac Apple Store asks me to connect with an account witch is not mine...

In Store > See Account my email is here but when I click on "Download Mavericks" Mac Apple Store says me :

"Connectez-vous à iluhin83@gmail.com pour mettre à jour les applications pour ce compte." (I'm French)

if I disconnect my account, Mac Apple Store asks me to put the password for iluhin83@gmail.com but it's not my account and I don't know who he is, and I can't change the email to connect me with MY account...

Help me... Pleaaaase .....

Thanks