Can't add the Payapl express checkout: error

Hi,

If i click install of the paypal express checkout, it show this error:
NOTE: You already have the PayPal Website Payments Standard module installed. You should REMOVE it if you want to install Express Checkout.

But I don't have any other module installed! How can I fix it?

Thank you

Um ... so, what color is the dot, if any, beside each of the PayPal modules?