This is the search page of Windows SharePoint Services V3.0 search and it is pretty much set in stone. It is not as flexible as a MOSS 2007 search center where you can customize the search web parts, search scopes and much more. WSS search only allows you to search single sites and sub-sites. Cross site search is not supported - you will need an Enterprise Search solution to do that.
Now, I guess you do not want or need to invest in MOSS 2007. But you could consider setting up a new Search Server 2008 Express (free) next to your WSS server. This gives you Enterprise search capabilities at a low cost. Let the MSS 2008 index all your WSS site collections and let the users search from a search center site on the MSS 2008 server.
One downside, however, is the small search box on your WSS sites will still point to the OSSSearchResults.aspx page. You will need to install another search box to direct users to the MSS 2008 search center.