I understand you have already said that the page file had been disabled but I wrote the following a couple of days ago but just hadn't posted it yet so I thought I would just post it as I had written it.
The most likely reason why you are receiving the
Your computer is low on memory message is because the applications you have running are unable to allocate the virtual memory they need because either you have disabled the paging file or the paging file isn't large enough for your workload. In the picture you have posted, in Task Manager and under the
System heading and then in line with
Commit (MB), the very first value is the commit charge current which represents the amount of committed virtual memory processes which are currently active have allocated. The second value is the commit charge limit which is based on roughly the amount of physical memory plus the size of the paging files and this represents the maximum amount of committed virtual memory processes can allocate at any one time.
If your paging file is not large enough to support the committed virtual memory requirements of your workload, your processes won't be able to allocate the virtual memory they want and will fail to run correctly. The system where I took the images below has 4GB of RAM and the paging file has been disabled to quickly illustrate what happens when you hit the system commit limit. The same would also apply if I had a paging file though, it would have just mean I would have needed to increase the workload of the system.
If you would like to manually size the paging file and are willing to take the time out to monitor the committed virtual memory requirements for your workload, this article
here will help you out. If not, letting Windows manage the size of the paging file should be sufficient.