One way to do it use stsadm.exe
Use Create web command and create the url.
Bacup the WSS site  you want renamed using stsadm.exe
Restore the wss site on the url  path you created.
Delete the site you wanted to rename.

I've also done this in FrontPage 2003. If you open the site,
click "tools" and "site settings". Under the "general" tab, change
the "web name" to what you want (in your case, change  "Project
Phoenix" to "Project Arthur") and "apply".

It seems to have worked for me, but I'm probably the least technical
person in this discussion group; I defer to the experts!