Windows 7 All-in-One ISO Creation Guide

Requirements before we begin:

Windows Automated Installation Kit
RT Seven Lite
Windows 7 x86 and Windows 7 x64 ISOs or DVDs or what have you...
Windows 7 Enterprise editions optional (not included in steps, but easily inferred. If you can't figure it out, maybe you should learn more about basic computer usage before installing Windows 7 Enterprise).
Plenty of hard drive space. You're going to have images of around 9 operating systems (compressed and partial, but still over a GB each at least) in one folder, and then put them all in a single file at the end. This can easily take 30 GB.

Before we start, note that this guide does not include a means of attaining keys for any versions of these operating systems, and is designed entirely to allow computer geeks like myself to provide fresh, untainted installs of any copy of an up-to-date version of Windows 7 for whatever edition/processor the person we're helping has, or a trial version while they get a key themselves (or whatever you do).
This guide also assumes a familiarity with RT7 Lite, and at least a basic understanding of command line input.

For each version (starter through ultimate x64), you must create a streamlined WIM. The order doesn't matter. Just use RT7 like normal, integrating the SP into each one you do. If you want any other updates, tweaks, or whatever, do them. You can do different settings for each version (except Unattended which is an XML file and not part of the WIM). Don't bother with ISO-Bootable, you're not gonna make a disc, you just need the WIM files. After you hit apply, check Step 2 for what to do next.
Choose Build Current Image Only. Export settings if you're going to be using the same settings, so that you can easily reload the same settings for each of the 9 times you'll be doing this. Hit Commit and let it do its thing.
Close RT7 when it's finished, don't do anything more in it when a version has been created. Simply go to the Sources directory of the Installer (or temp path if you extracted from ISO) and grab the INSTALL.WIM file. Cut it and paste it into a folder for all the WIM files. Put a new copy of your original INSTALL.WIM file back in that folder so you can do the same thing again for the next version. It'll probably be best to rename the INSTALL.WIM you moved to another folder after which edition you made, for example Win7SP1x86_STARTER.WIM or Win7SP1x64_ULTIMATE.WIM.
After you've done all this nine times over, you should end up with 9 WIM files in a folder. Now it's time to put them all back into a single WIM file. Open the Deployment Tools Command Prompt in the Windows AIK Start Menu folder, and enter the following lines, replacing paths as needed:

Imagex /export "D:\AIO\WIMs\Win7SP1x86_ST.wim" 1 "D:\AIO\DVD\sources\install.wim" "Windows 7 STARTER" /compress maximum
Imagex /export "D:\AIO\WIMs\Win7SP1x86_HB.wim" 1 "D:\AIO\DVD\sources\install.wim" "Windows 7 HOMEBASIC" /compress maximum
Imagex /export "D:\AIO\WIMs\Win7SP1x86_HP.wim" 1 "D:\AIO\DVD\sources\install.wim" "Windows 7 HOMEPREMIUM" /compress maximum
Imagex /export "D:\AIO\WIMs\Win7SP1x86_PRO.wim" 1 "D:\AIO\DVD\sources\install.wim" "Windows 7 PROFESSIONAL" /compress maximum
Imagex /export "D:\AIO\WIMs\Win7SP1x86_ULT.wim" 1 "D:\AIO\DVD\sources\install.wim" "Windows 7 ULTIMATE" /compress maximum
Imagex /export "D:\AIO\WIMs\Win7SP1x64_HB.wim" 1 "D:\AIO\DVD\sources\install.wim" "Windows 7 HOMEBASIC (x64)" /compress maximum
Imagex /export "D:\AIO\WIMs\Win7SP1x64_HP.wim" 1 "D:\AIO\DVD\sources\install.wim" "Windows 7 HOMEPREMIUM (x64)" /compress maximum
Imagex /export "D:\AIO\WIMs\Win7SP1x64_PRO.wim" 1 "D:\AIO\DVD\sources\install.wim" "Windows 7 PROFESSIONAL (x64)" /compress maximum
Imagex /export "D:\AIO\WIMs\Win7SP1x64_ULT.wim" 1 "D:\AIO\DVD\sources\install.wim" "Windows 7 ULTIMATE (x64)" /compress maximum

This final INSTALL.WIM you create will contain all the setups you created earlier, and still retain a decently small size. Now put the final WIM in the Sources folder of a fresh copy of an extracted ISO (you can just copy all the files off an x86 disc into a folder). If you want to add any Unattended settings, copy the Autounattend.xml file to this folder as well.
Last step! If you're making a DVD or ISO, follow these instructions.
Turn this folder into a bootable ISO:
1. Create a text file called bootorder.txt with the following contents:
  
  boot\bcd
  boot\boot.sdi
  boot\bootfix.bin
  boot\bootsect.exe
  boot\etfsboot.com
  boot\memtest.efi
  boot\memtest.exe
  boot\en-us\bootsect.exe.mui
  boot\fonts\chs_boot.ttf
  boot\fonts\cht_boot.ttf
  boot\fonts\jpn_boot.ttf
  boot\fonts\kor_boot.ttf
  boot\fonts\wgl4_boot.ttf
  sources\boot.wim
  
  (New line at the end is important!)
2. Using the command prompt which should still be open from step 4, run the following command, replacing paths again as needed:
  oscdimg -m -n -yoD:\AIO\bootorder.txt -bD:\AIO\DVD\boot\etfsboot.com D:\AIO\DVD D:\AIO\Win7SP1_AIO.iso
If you're making a bootable Flash drive, simply copy the contents of the folder you created from the fresh ISO and the new INSTALL.WIM to a Bootable flash drive.