Windows XP text-mode installer, is it really a DOS application?

When first installing Windows XP. I am presented with a textual interface.

What API does t开发者_如何学运维his textual installer use?

• 16-bit DOS application
• 32-bit DOS application
• Windows Native API
• Standard Win32 API

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Going thorough a disassembler I have found the following...

This applies to a Windows XP Service Pack 2 installer...

I386\SETUPLDR.BIN

• The very beginning of text-mode setup where it asks for and loads basic drivers.
• It also asks about the recovery console.
• This is bootloader style code. Not a PE executable. I am unsure if it is 16-bit or 32-bit code.
• Uses ASCII strings.
• It actually takes about a minute to run, loading all the CD drivers and such.
• I am unsure if the Windows Kernel is running at this point.

I386\USETUP.EXE

• Windows kernel is definately running at this point.
• Displays the License agreement, the partitioner, and copies files to disk.
• 32-bit native mode PE executable. Native mode means unmanaged (i.e. not a .NET executable), BUT it also means that the executable ONLY uses the Native undocumented ntdll.dll API.
• This executable is Unicode aware and uses Unicode strings.