How to decompile xbox 360 exe files?

[atom0s]

Ok for this, the xex is compressed, so you need to decompress it first.
Attached to this post is xextool v6.3. (use with caution, no idea if its trusted/safe, I use it in a VM)

Put xextool and the exe you supplied in the same folder, open command prompt and run:

xextool.exe -c u SpeedMilestoneOpt-enUS.exe

This will decrypt/decompress the file.

Next, use the attached python scripts for IDA which are loaders. Place the .py's inside of <Path to IDA>/loaders/

These scripts are the old idaxex version before it was turned into a plugin. (However, the plugin does not work/support the 32bit version of IDA.) I've modded this script to work with IDA 7.5 (Python 3.9.x).

You should see the option to run the file with the Python script as the loader now in IDA. Let that run and then you should be able to apply the .pdb after it loads.