This post is 100% plagiarized from Steffen's post at Apache Lounge, I just want it here too
http://www.apachelounge.com/viewtopic.php?t=2060
Use the following command to perform the extraction:
msiexec /a filepath to MSI file /qb TARGETDIR=filepath to target folder
Replace filepath with the path of the MSI file.
Replace filepath to target folder with the path of the folder you want the files to be extracted to
Example: msiexec /a c:\myfile.msi /qb TARGETDIR=c:\myfolder
Press Enter and you're done. The files within the MSI installer will be extracted to the folder you specified.