I've actually gotten an old website up to PR 6. Don't ask me how. I stopped working on it about half a year before it got to PR 6, that means no new content, no added backlinks, etc. On the topic of backlinks, I didn't have many of them either. In the end, I just used the site to link to my other sites, but unfortunately the host (which was free, another thing to surprise me with the PR) died.