Script by Lars_k
Tested with opsi 4.0.1
Test with W7 32 & 64 Bit
The installion-files available Download from : http://www.7-zip.org/

Tree:

Bild.png ( Product Picture)
setup.ins
uninstall.ins
Folder Depot
in Depot
Depot\7z920.exe
Depot\7z920-x64.msi

[Initial]
ExitOnError=true
StayOnTop = true
 
[Actions]
requiredWinstVersion >= "4.10.5"
 
DefVar $ProductId$
DefVar $ExitCode$
DefVar $NTVersioninfo$
DefVar $32bitfile$
DefVar $64bitfile$
DefVar $uninstallstring$
DefVar $Parameter$
SetLogLevel=6
Set $32bitfile$ ="7z920.exe"
Set $64bitfile$ ="7z920-x64.msi"
; ----------------------------------------------------------------
Set $ProductId$       = "7 Zip 9.20"
; ----------------------------------------------------------------
 
ShowBitmap  "%ScriptPath%\bild.png" $ProductId$
Message "Installiert  " + $ProductId$ + " ..."
 
if not (HasMinimumSpace ("%SYSTEMDRIVE%", "50 MB"))
	LogError "Es ist nicht genügend freien Speicherplatz auf dem Laufwerk : %SYSTEMDRIVE%  vorhanden."
		isFatalError
endif
 
; OS Version ermitteln  > Win2000
Set $NTVersioninfo$ = GetMsVersionInfo
 
if not ( $NTVersioninfo$ >= "5.1" )
	LogError "Kein Komp. Betriebssystem vorhanden." 
		isFatalError
endif
 
; 64 Bit OS 
if GetSystemType = "64 Bit System"
	comment " 64 Bit System"
	Sub_uninstall
	Winbatch_7zip64bit
	comment " 7Zip wird installiert"
	Sub_check_exitcode
endif
 
; 32 Bit OS 
if GetSystemType =  "x86 System"
	comment " 32 Bit System"
	Sub_uninstall
	Winbatch_7zip32bit
	comment " 7Zip wird installiert"
	Sub_check_exitcode
endif
 
 
[Winbatch_7zip32bit]
%ScriptPath%\depot\$32bitfile$ /S 
 
 
[Winbatch_7zip64bit]
msiexec /i %ScriptPath%\depot\$64bitfile$ /qn
 
 
[Winbatch_remove]
"$uninstallstring$" $Parameter$
 
 
[Sub_uninstall]
; Prüft ob eine 64 Bit Version installiert ist.
if ( FileExists("%ProgramFiles64Dir%\7-zip") )
	comment "64 Bit Version gefunden"
	Set $uninstallstring$ = "MsiExec"
	Set $Parameter$ = " /X{23170F69-40C1-2702-0920-000001000000} /qn"
	Winbatch_remove
	Sub_check_exitcode
	comment "64 Bit Version deinstalliert"
endif
 
; Prüft ob eine 32 Bit Version installiert ist.
if ( FileExists("%ProgramFiles32Dir%\7-zip") )
	comment "32 Bit Version gefunden"
	Set $uninstallstring$ = "%ProgramFiles32Dir%\7-zip\Uninstall.exe" 
	Set $Parameter$ = " /S"
	Winbatch_remove
	Sub_check_exitcode
	comment "32 Bit Version deinstalliert"
endif
 
 
[Sub_check_exitcode]
comment "Test for installation success via exit code"
set $ExitCode$ = getLastExitCode
; informations to exit codes see
; http://msdn.microsoft.com/en-us/library/aa372835(VS.85).aspx
; http://msdn.microsoft.com/en-us/library/aa368542.aspx
if ($ExitCode$ = "0")
	comment "Looks good: setup program gives exitcode zero"
else
	comment "Setup program gives a exitcode unequal zero: " + $ExitCode$
	if ($ExitCode$ = "1605")
		comment "ERROR_UNKNOWN_PRODUCT	1605	This action is only valid for products that are currently installed."
		comment "Uninstall of a not installed product failed - no problem"
	else
		if ($ExitCode$ = "1641")
			comment "looks good: setup program gives exitcode 1641"
			comment "ERROR_SUCCESS_REBOOT_INITIATED	1641	The installer has initiated a restart. This message is indicative of a success."
		else
			if ($ExitCode$ = "3010")
				comment "looks good: setup program gives exitcode 3010"
				comment "ERROR_SUCCESS_REBOOT_REQUIRED	3010	A restart is required to complete the install. This message is indicative of a success."
			else
				logError "Fatal: Setup program gives an unknown exitcode unequal zero: " + $ExitCode$
				isFatalError
			endif
		endif
	endif
endif

[Initial]
ExitOnError=true
StayOnTop = true
 
 
[Actions]
requiredWinstVersion >= "4.10.5"
 
DefVar $ProductId$
DefVar $ExitCode$
DefVar $NTVersioninfo$
DefVar $uninstallstring$
DefVar $Parameter$
SetLogLevel=6
 
; ----------------------------------------------------------------
Set $ProductId$       = "7 Zip 9.20"
; ----------------------------------------------------------------
ShowBitmap  "%ScriptPath%\bild.png" $ProductId$
Message "Deinstalliert  " + $ProductId$ + " ..."
 
; OS Version ermitteln  > Win2000
Set $NTVersioninfo$ = GetMsVersionInfo
 
if not ( $NTVersioninfo$ >= "5.1" )	
	LogError "Kein Komp. Betriebssystem vorhanden."
		isFatalError
endif
 
; 64 Bit OS 
if GetSystemType = 	"64 Bit System"
	comment " 64 Bit System"
	comment " 7Zip wird entfernt."
	Sub_uninstall
endif
 
; 32 Bit OS 
if GetSystemType =  "x86 System"
	comment " 32 Bit System"
	comment " 7Zip wird entfernt"
	Sub_uninstall
endif
 
 
[Winbatch_remove]
"$uninstallstring$" $Parameter$
 
 
[Sub_uninstall]
; Prüft ob eine 64 Bit Version installiert ist.
if ( FileExists("%ProgramFiles64Dir%\7-zip") )
	comment "64 Bit Version gefunden"
	Set $uninstallstring$ = "MsiExec"
	Set $Parameter$ = " /X{23170F69-40C1-2702-0920-000001000000} /qn"
	Winbatch_remove
	Sub_check_exitcode
	comment "64 Bit Version deinstalliert"
endif
 
; Prüft ob eine 32 Bit Version installiert ist.
if ( FileExists("%ProgramFiles32Dir%\7-zip") )
	comment "32 Bit Version gefunden"
	Set $uninstallstring$ = "%ProgramFiles32Dir%\7-zip\Uninstall.exe" 
	Set $Parameter$ = " /S"
	Winbatch_remove
	Sub_check_exitcode
	comment "32 Bit Version deinstalliert"
endif
 
 
[Sub_check_exitcode]
comment "Test for installation success via exit code"
set $ExitCode$ = getLastExitCode
; informations to exit codes see
; http://msdn.microsoft.com/en-us/library/aa372835(VS.85).aspx
; http://msdn.microsoft.com/en-us/library/aa368542.aspx
if ($ExitCode$ = "0")
	comment "Looks good: setup program gives exitcode zero"
else
	comment "Setup program gives a exitcode unequal zero: " + $ExitCode$
	if ($ExitCode$ = "1605")
		comment "ERROR_UNKNOWN_PRODUCT	1605	This action is only valid for products that are currently installed."
		comment "Uninstall of a not installed product failed - no problem"
	else
		if ($ExitCode$ = "1641")
			comment "looks good: setup program gives exitcode 1641"
			comment "ERROR_SUCCESS_REBOOT_INITIATED	1641	The installer has initiated a restart. This message is indicative of a success."
		else
			if ($ExitCode$ = "3010")
				comment "looks good: setup program gives exitcode 3010"
				comment "ERROR_SUCCESS_REBOOT_REQUIRED	3010	A restart is required to complete the install. This message is indicative of a success."
			else
				logError "Fatal: Setup program gives an unknown exitcode unequal zero: " + $ExitCode$
				isFatalError
			endif
		endif
	endif
endif