customize WP icon

hey there,
I am trying to change the Word Press “W” that appears next to my blog in my admin panel and also when people subscribe to my blog…

is this a Favicon issue? I thought Favicons popped up in the browser window, but maybe they do both?

WP is not hosting my blog, so I don’t have the apparently nifty setting you can set from the Settings page.
thanks for pointing me in the right direction!
tracy