Hey guys, if anyone else has crashing with "Your computer is running low on memory", monitor losing connection, other general weirdness, and setting lighting to low doesn't do anything, maybe try the following suggestion (source:
https://www.reddit.com/r/darksouls3/comments/4edfpm/pc_tech_support_megathread/d1z9ot9)
For reference I have 6GB of RAM, which I was worried might be the issue, but the games been running fine at around 40 - 60 FPS on max settings (GTX 780) aside from the crashing, which I think this fixed.
For Windows 8 (and probably 10):
-search "This PC"
-right click "This PC" and select Properties
-select "Advanced System Settings" in the sidebar
-Select the advanced tab
-under Performance, click "Settings"
-select the Advanced tab
-under Virtual Memory, select "Change"
-de-select "Automatically manage paging file size for all drives".
-Select your primary drive (probably C

and select Custom Size
How much you set for the virtual memory here is up to you, people had results with at least 2048MB but I set that as the initial size, and set the maximum size to 4093MB. I had two drives so I set both of them to have this initial and maximum size.
This alone did not fix my crashes, so I also tried the borderless window fix even though it didn't seem like it would do anything. Turns out, for me it did! I was able to play for a whole hour (gasp) without crashing, and I stopped just because I have other things to do. First time I've quit the game on purpose lol. Before that I would literally crash after at most five minutes in game in Lothric, usually with a low memory warning or with my computer completely shutting down and restarting on its own (not a good sign).
The third party app I used for bordered windowless was WindowedBorderlessGaming. It came in a zip, and running the executable was enough to get the game to run in windowed borderless mode. Like I said, since then I haven't had any issues (granted I've only played an hour since then)
JaseC, could we mention this fix in the first post? I was getting pretty discouraged when the only fix I could find was setting Lighting to low, and was very relieved to find this fix buried in the reddit tech support megathread! It sounds like there are other people having this issue, though not as many as the lighting problem.
edit:
Give this a shot, hopefully it'll fix the issue for you as well!