I have just looked into MSI 3.1.
You can safely extract WindowsInstaller-KB893803-v2-x86.exe using WinRAR.
Msi.exe + msi.dll doesn't require too many new apis:
MSI.EXE
Kernel32:GetUserDefaultUILanguage -simple xor eax,eax ret should do the trick

Ntdll:NtQueryInformationProcess
advapi32:ConvertSidToStringSidW
but on the other hand... in update\langspecific\ there are update.exe and spuninst.exe which require 40+ new exports

. Are those files needed for MSI 3.1 to work?
nicke85
If you wanted to fool MSI based installers you should add the following entry to C:\WINDOWS\KUPVER.INI:
CODE
[Override]
C:\WINDOWS\SYSTEM\MSIEXEC.EXE=winxp
However this doesn't seem to work for me:
QUOTE
The Windows Installer service could not be accessed. Contact your support personnel to verify that the Windows Installer service is properly registered.
Do you guys have any clues how to make MSI 2.0 work in NT mode ?