I would just download the web2py_src.zip and unpack it in a different directory and then run it from that directory
python web2py.py do the simple app in admin and check the result. I believe the simple app builder is just an unpack and rename of the welcome app - the w2p file in the base of your web2py install is teh basis for that application construction. I would guess that user is somehow embedded in the welcome app sqlite database. Maybe this person found you machine and registered when you were in early stages of installation using the welcome app?
