The default users are root and visitor (or in the case of the initial live CD, archlinux). In ISOs dated before 1/9/2013, both of these had no password. In ISOs dated at 1/9/2013 or later, the password for root is treevitals and the password for visitor is visitor.
Because the default .xinitrc takes a session executable as $1, you would need to run this in place of startx without CLI arguments.
startx ~/.xinitrc <window manager, most likely pekwm>
In the case of xinit, replace it with the command below.
xinit <window manager, most likely pekwm>
Chances are (if the iso is dated before 1/9/2013) that you forgot to select Pekwm from the session list. You should be able to log in now.