Is it a single .exe install or a full install? Did you use a software distribution tool, such as Altiris, or are you logged into the computer and installing manually?
The log file will go into the temp folder based upon method of installation. If you're logged into the computer, the log file will go into the temp folder for that user. If you use a software distribution tool, the log file will go into C:\Windows\Temp.
Also, I've seen computers that won't take a single .exe installation, but it will install just fine with the full installation.
Sometimes it helps to export a full installation and remove the /qn from the setup.ini file to see what the problem is. Log files may have an entry for Error 1603, but a visible installation may say there are pending system changes that require a reboot before SEP can be installed.