https://sureai.net/forum/viewtopic.php?t=3007
sir wrote:The installer's from the torrent, so it's fine. Torrents have built-in integrity checking.
I just copied all of Oblivion's .BSA files to Nehrim\Data, and the game starts now, so I suppose my guess was correct: the installer had more problems than just not copying the executable. Would be nice to figure out what's actually going on, because who knows what else might be amiss...