Stolen from the 4e Discord as well.
CHARACTER BUILDER INSTALLATION INSTRUCTIONS *** (updated 2023-Jan-11)
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INSTALLING CHARACTER BUILDER AND CBLOADER 1.4.6.1:
1. Get the Character Builder installer and update from
https://www.dyasdesigns.com/CharacterBuilder/CB-oldbuilder.zip
2. Extract the file from Step 1. It should create a folder named CB-oldbuilder.
3. Get the 1.4.6.1 CBInstaller.exe and CBLoader.zip from
https://github.com/CBLoader/CBLoader/releases/latest and save them in the CB-oldbuilder folder created in step (2), or save them elsewhere and move them there. This folder should contain these files: CBLoader.zip, CBInstaller.exe, Character_Builder_Update_Oct_2010.exe, and ddisetup2009April.exe.
4. Run CBInstaller.exe (Windows may complain, and you'll probably have to approve several elevated permissions)
5. Delete the "Character Builder" shortcut it creates automatically. (Some people have reported this shortcut does not get created for them; that's fine, move on if that's the case.)
6. Move everything from the CB-oldbuilder folder created in step (2) into %APPDATA%\CBLoader\ (this folder was created during step (4), and is usually found at C

Users\[your username]\AppData\Roaming\CBLoader\) (see Note below) If the Builder installed properly, but this folder was not created, you can create this folder yourself before this step, but it should not be necessary.
7. Run CBInstaller.exe from %APPDATA%\CBLoader\. This should properly install CBLoader and create a "CBLoader" shortcut.
Note: On Windows, the AppData folder is usually Hidden unless you have changed your Explorer View Settings to "Show hidden files and folders". You can also directly access your AppData on Windows by entering into search: %APPDATA% (with the % symbols) and hitting Enter.
The installation may create another CBLoader.zip file on the desktop when running the shortcut from the desktop the first time. If it does, this extra file can be removed.
Once 1.4.6.1 is installed correctly, it will report itself as 1.4.6 once the Builder's loaded. You can confirm it is installed by creating a character, and looking on the Class tab. The first class should be "Binder" if it has been installed correctly.
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EXPECTED FINAL STATE:
The final state of a properly-installed Character Builder + CBLoader should be:
C

CharacterBuilder - the builder program itself. Never touch this folder.
C

Users\[your username]\Documents\ddi\CBLoader - .part and .index files. This is where you put homebrew or other content you're adding.
C

Users\[your username]\AppData\Roaming\CBLoader - this is the actual installation location of CBLoader, and you should be running CBInstaller.exe from this folder, using a shortcut. (this is the same location as entering %APPDATA% into Windows search and opening the CBLoader folder)
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UNINSTALLING THE CHARACTER BUILDER AND CBLOADER:
When uninstalling, always start by going to Windows Add/Remove Programs, and uninstalling from there first before attempting any manual uninstallation. Uninstall both "CBLoader" if it appears (older versions might), and "Character Builder".
Please see our CBLoader Troubleshooting Guide
https://github.com/CBLoader/CBLoader/wiki/Troubleshooting for any additional issues with CBLoader Installation or Use.
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RUNNING THE CHARACTER BUILDER AND CBLOADER ON A MAC:
While we don't have a step-by-step guide for using the Character Builder on a Mac, it is possible on some Macs using Windows emulation.