Here I published a tutorial for it and many others programs. Please comment on the blog if you have questions.

http://it-grund.blogspot.com/2012/04/how-to-deployinstall-silently-and.html

msiexec.exe /i "7z920.msi" /qn /norestart

x86 using MSI from download supressing restart, using default msi name.

msiexec.exe /i "7z920-x64.msi" /qn /norestart

x64 using MSI from download supressing restart, using default msi name.

SMS files for import into SCCM 2007 Vista x64 and Win7 x64 using Package Definition Format

------------

[PDF]
Version = 2.0

[Package Definition]
Name = 7zip
Version = 9.20 x64
Publisher = GNU
Language = English
Programs = 7zipSetup

[7zipSetup]
Name = 7zip 9.20 x64 Installation
CommandLine = msiexec.exe /i "7z920-x64.msi" /qn /norestart
SupportedClients = Win NT (x64)
Win NT (x64) MinVersion1=6.00.0000.0
Win NT (x64) MaxVersion1=6.00.9999.9999
Win NT (x64) MinVersion2=6.10.0000.0
Win NT (x64) MaxVersion2=6.10.9999.9999
UserInputRequired = False
RemoveProgram = True
AdminRightsRequired = True
CanRunWhen = AnyUserStatus
EstimatedRunTime = 15
EstimatedDiskSpace = 10MB

MSI lines can be modified to fit your environment. 
MSI deployment msiexec.exe /q /i "<filename.msi>"

Optional 

INSTALLDIR="C:\Program Files\7-Zip" to Change Install Directory
/qn or /qb can be substituted for /q 
/norestart can be added.

SMS files for import into SCCM 2007 XP x86, Vista x86 and Win7 x86 using Package Definition Format

------------

[PDF]
Version = 2.0

[Package Definition]
Name = 7zip
Version = 9.20 x86
Publisher = GNU
Language = English
Programs = 7zipSetup

[7zipSetup]
Name = 7zip 9.20 x86 Installation
CommandLine = msiexec.exe /i "7z920.msi" /qn /norestart
SupportedClients = Win NT (i386)
Win NT (I386) MinVersion1=5.10.0000.0
Win NT (I386) MaxVersion1=5.10.9999.9999
Win NT (I386) MinVersion2=6.00.0000.0
Win NT (I386) MaxVersion2=6.00.9999.9999
Win NT (I386) MinVersion3=6.10.0000.0
Win NT (I386) MaxVersion3=6.10.9999.9999
UserInputRequired = False
RemoveProgram = True
AdminRightsRequired = True
CanRunWhen = AnyUserStatus
EstimatedRunTime = 15
EstimatedDiskSpace = 10MB

For More Specifics on modifying this file for your environment see. 
About Package Definition File Format. 
http://technet.microsoft.com/en-us/library/bb632631.aspx 

MSI lines can be modified to fit your environment. 
MSI deployment msiexec.exe /q /i "<filename.msi>"

Optional 

INSTALLDIR="C:\Program Files\7-Zip" to Change Install Directory
/qn or /qb can be substituted for /q 
/norestart can be added.

32-Bit MSI can be found at http://www.7-zip.org/download.html