Crash Free may not be possible but I have managed to greatly reduce the amount I have crashed and the severity of those crashes.First my system when I started.
3 GHZ Dual core processor
Nvidia GTX+ 9800
4 GB ram
SoundBlaster Value 5.1 (12 - 15 years old) - Then to RealTek HDAudio 7.1
So when first running it was having real problems ,even blue screens of death ,but wasn't sure why ,had never updated my Bios as that has its risks but no matter what I tried nothing seemed to work.So updated it (thank god my isp provider is ranked as best in North America)had to do it online.Anyway it improved less crashes.Next was my soundcard ,I have onboard Realtek HD Audio but was using my Soundblaster card cause there are issues with missing windows files and Realtek anyway found a posting on my mobo's site that explained how to get around it ,also updated all my other drivers for my system.Anyway started it up and noticed a big improvement.After that started tinkering around with the settings in the game and settled on a 1400 - 900 widescreen resolution ,HDR, basically all shadows turned off except trees (shadows at 512) ,all distance viewing on ,and most the effects in diary off ,except for the essential ones.Also its a good idea in any game really to have the game resolution match up with your system resolution and as Nehrim run off the Oblivion engine and takes its settings from Oblivion its helpful to match that up as well when you start Oblivion that one time so Nehrim will have all the files it needs.You may not think it would make a difference but a friend of mine once told me windows has the habit of checking resolutions built in its OS and it helps if all the resolutions are the same.Now one final thing Nehrim is a game basically running over another game (Oblivion) and as such its a program utilizing another program ,well from playing Third Age Total War ,a Medeival 2 Total War conversion I was informed that many Virus checkers will look upon this as a virus because it shares many of the mimicry scripts that viruses use to infect your system but because its not a virus it doesn't know what to do with it ,so it just keeps checking and checking til you crash.Anyhoo turned off my virus checker and voila can have crash free sessions lasting from 4 - 12 hours .Still ocassionally crashes but its much better ,much much better. And the crashes are just CTD no more blue screens of death.
Now when I play Its a matter of me running around like a mad man or clicking on doors and things too fast that may or may not cause it to crash all I have to do is slow up to let the processing catch up ,and with a new clean install and maybe using stutter removal I may mitigate that to some degree.All in all I'm pretty pleased with it now.
Hope this helps
PS: My install of Nehrim is in its own dir on the C: drives and its not a steam version of Oblivion I have
PPS: Also just so you know I'm using regular old QTP3 , not QTP3Redimized with its optimized meshes a,d that alone would see my game performance improve