Whether you want to know what an MSI contains or if you want to just extract a single file from an MSI you have, at least, two alternative ways of doing so.
Your first choice is to open a command prompt window and type:
msiexec /a <name>.msi
The /a switch -administrative privileges- option works with most of MSI, but in some MSI priviledges is disabled, so your second choice is to use the /a switch with the TARGETDIR public property in silent mode.
So, your final commnad will be something like this.
msiexec /a <name>.msi TARGETDIR=<path> /qb
For more command line that are available with Windows Installer consult the corresponding page of the MSDN Library, here.