Mine used to crash too, but I fixed it. It had nothing to do with graphic settings, but with the fact that the game ran out of memory after some time. Here's the fix.
1. Go to start and type in "cmd", no quotes. Press enter and a black window should appear.
2. Enter the following text, without the quotes : "bcdedit /set IncreaseUserVa 3072" and press enter
3. Restart the PC
This increase the value of page pool memory the OS will allow the game to use, and it did not crash for me anymore. The longest session I used to have was 40-50 minutes until it crashed. Now I've played for 3 hours with no issues.

To cancel this, just type in "bcdedit /set defaultuserva"

Hope this helps.

Cheers!

Having run on a Intel Celeron 1.8 Ghz, Radeon X 1050 machine from 2002 until 2011, I know a thing or two about optimization.
1. CCleaner - Use it to clear your C partition, defrag your hard-drive. If it is a slow hard-drive, the game will run slow. That is not because the data is processed in it, but because it is slow to send data to be processed. You can also use this to delete old, unused registries and corrupt files. Check out all the options, it is really easy to use.
2. Gboost, a very useful, small, totally free tool that I use myself. All it does is it closes processes and services that are not necessary, it has options to select features you want turned on or off.
3. Power Strip, another very useful totally free tool that you can use to boost your graphic card performance. I cannot use it myself as I currently own a notebook, but on my old PC it worked miracles. One thing I remember for sure, I was playing STALKER : Call of Prypiat. Vanilla game with no tools, 10-12 FPS average, lots of stuttering. After disk defrag, using Gboost and tweaking game grass and shadow a bit, 18-20 FPS. The game I played on medium to low settings, on a 1280x1024 resolution. After I used Power Strip turned on to the max, 23-28 FPS, playable. Thing is, Power Strip overclocks your graphic card - wait for it - in the limits it was designed to work! No actual overclock, but unleashing full potential. Terribly good tool!
4. Vsync, AA and Anti-Sotropic filtering are FPS killers. Turn these off if you can. Also, shadows, grass, decals, depth of field, ambient occlusion, motion blur, all are FPS killers. Turn these off too.
5. If you are willing to invest some money into your computer, I would say go for an SSD. 60 GB SSD only for gaming. That should improve the performance of your games a lot.

That is about all the safe, tested ways I can fully guarantee for that will improve your performance. I know some others, but they are not at all same and might screw up everything. I tweaked around Mount and Blade once on my machine. I managed to screw up all the texture on my first try

Thank you very much for the file! And thank you for telling me about the mod, though I found it right before I read your message, it's very good. The file works fine, I modified the amounts as 999 seems a little bit to much Thank you for your help!

I will eventually get used to saving a lot. One more question though, I would like to increase item stack sizes. I have read that I have to extract the .bif files and modify some of the .2da files inside them, and for that I downloaded the unBIF tool by Csimbi. I select the main.key file, which governates the baseitems.2da and I choose to extract that file. But no matter where I chose to extract it, and yet no matter the .bif file I want to extract, nothing happens. I have this issue in every RPG game where I don't know much, I just collect everything and I usually keep it until I can figure out what is worth keeping and what is not. I am ok with the actual sizes, but since I like to explore a lot and gather tons of stuff I'd like some more space at least until I can figure it out myself.
Do you have any idea on what could be going wrong about this?

Alright, I have played RPG's and I usually forget to save though I always bear in mind that I need to save. I will try turning off the autosave though I haven't noticed the game had one Nevertheless, I am greatly moved by this nice community I never thought could have existed. I'd like to be a part of it and help as much as I can.