I've used Brinkster for hosting several websites on the cheap... and recently I wanted to take one of those sites and add DotNetNuke (DNN) on top of it, without converting any of the pages to DotNetNuke skins and tab pages.

What I did was rename the current site's Default.aspx to Default_MySite.aspx so that DNN's Default.aspx could take it's place. Then, I added a bit of code in DNN's Default.aspx to take care of rerouting any requests to “MySite”...

If Request.Url.AbsoluteUri.ToLower.IndexOf("mysite") <> -1 Then
      Response.Redirect("default_mysite.aspx")
End If

After a quick check to be sure that none of DNN's project files had the same name as the existing site, I copied the remaining DotNetNuke files on top of the existing site, built, and released. I also needed to make a request to Brinkster Support to add privileges for the ASPNET Machine account to my webroot and all subdirs (as this is required by DotNetNuke). This retrofit allowed me to quickly add DNN to an existing Brinkster hosted account and still preserve the existing site.