erasing all traces of a program from your computer

[Tellos Athenaios]

You could try using Process monitor (Procmon). It's a free former Sysinternals now Microsoft tool that's somewhere on their technet site and rather invaluable when modding CA games as well. Process monitor will be able to tell what registry keys and files the program is looking at on startup, although some types of DRM might make the Ubisoft game commit ritual suicide in protest. However, since it probably is some weird DRM type software thing you will likely be able to find out a few things from the logs before a crash happens:

What files the game needs to launch its DRM, what registry keys the DRM is looking at prior to crashing and what files the DRM is looking at prior to crashing.

These clues in turn should point you to the particular DRM software being used, so you can then go on and hunt the web for clues on how to remove it or fix your problem. In case you are lucky the problem isn't with the DRM, you'll get a full trace of events and you can then inspect that to see where the game is crashing and what stuff must all be removed to completely uninstall it. Then you can move on to purging all its traces from your PC and installing it as if you never used it before.