The official IE7 installer doesn't integrate via standard methods properly (I think there is a lack of appropriate icons for some things). Same with Windows Media Player 11. However the issues with IE7 don't affect the install of the OS - but rather the actual install of the product. The reason is that they depend on Windows Installer 3.
You need to use an IE7 Addon from the RyanVM.net forums. I like to use the alternative pack, but that's just my personal preference.
Well, winnt.sif gets used by CD based installs, unattend.txt gets used by remote installs. The reader for this file is very limited. In some cases, it doesn't matter what you put in the line - as long as it's not the default it will do the other thing. Be sure you change both winnt.sif and unattend.txt just in case (they should be identical).
Also be sure you've got the order right. I've noticed you've got the UnattendSwitch and OemPreinstall flip flopped. I don't think that this could cause a problem, but with such limited parsing of the file it is possible that getting them out of order could pose a problem. See the link I posted to get the correct order of things. I think there's a program out that will generate this file for you properly, but I can't seem to locate it. If I find it again I'll post it for you.
However, you've got the order of the tools right. It's just this OOBE problem. I recommend posting at the MSDN forums, they're probably more familiar with the OOBE problem (it's very fragile - breaks easily on windows install disks).