Here's how to add your company logo so it is inherited across your sites.

Browse to the top level of your site collection in the browser.

From The Site Actions Menu, Select View All Site Content

Select the Site Collection Images Library

Upload your Company Logo (companylogo.gif) - If required, approve this image.

Open SharePoint Designer 2007 and Select File, Open Site. Type the URL of the top level of your site collection.

Locate the master page gallery in the left pane. _catalogs\masterpage

Double click the default.master (you may be prompted to check it out - if so choose yes)

Search For: <SharePoint:SiteLogoImage id=”onetidHeadbnnr0″ LogoImageUrl=”/_layouts/images/titlegraphic.gif” runat=”server”/>

Replace With: <asp:Image runat=”server” id=”logo” ImageUrl=”< %$ SPUrl: ~sitecollection/sitecollectionimages/companylogo.gif %>/>

What the above does is replace the default (site by site) mechanism for replacing the company logo with a hard coded reference to the company logo which you uploaded to the Site Collection Images library.

By doing this, all pages which inherit from the top level default.master will be updated to reflect this change. Each time you create a sub site, simply inherit from the master page of the parent site collection.