Core has a subfolder here, there were already some reports/complaints from Steam user and hints how to get it working.
I also made a Core quickfixes thread to fix some of the bugs found after release of 0.49.
If possible, find you AoD installation somewhere in the Steam subfolder and copy all content over to a new folder, maybe c:\Games\AoD. Then try to run it from there. If Steam has not altered too much then it should be playable from there.