Thanks for the help. I tried, and used this:
...
<phase>FIRSTLOGON</phase><command>C:
\Systemupdate506-01-15-2015.exe</command></task></tasks><phase>FIRSTLOGON</phase><command>msiexec.exe /i C:
\logmein.msi</command></tasks></tasks></advanced_options><settings>
But still not working...
Does the msiexec.exe mean that I have to find the name of the .exe within the MSI? Or did I mess something else up?