"Your computer is low on memory" when its clearly not

My guess is, you can get rid of the problem for the desktop by making sure the display resolution is set to the monitor's native resolution (right-click on Desktop => Screen Resolution, select the recommended resolution in the "Resolution" drop down).

Makes the picture more crisp & clear, too.

This does not cure the games issue, of course.

Kindly report back here if this helped or not, it will assist in drilling down to the core of the issue.

Been getting this error for a couple of weeks now.  I'd get it playing games, running chrome, running Unity, and running other high intensive rendering programs.  Much like you though, when I'd check the resource monitor, I'd only see 33% memory usage.

Checking the Event Viewer I saw Windows reporting absurdly high usage memory usage (basically filling my RAM for a split second) from these rendering intensive applications at the time of the warning.  Afterwards, memory usage returned to normal.

After looking deeper, I found out that the video drivers the system was using were just plain wrong.  I might just be paranoid, but I suspect Windows Update silently updated my video drivers for my R9 280X from working drivers (which I installed myself when I bought the machine) to AMD Radeon 7900 series drivers from April, 2014.  I headed over to the support site for my card and downloaded the latest drivers and haven't seen a problem since.

My guess is that this problem exists with certain older drivers (and possibly some newer ARM/onboard chipset drivers as well) when using Windows 8.1.  I'll probably be disabling Windows Update's driver download feature out of paranoia.

Only problem, the post by PeterBaenzinger above was off-topic. The thumbs.db is unrelated to the original issue: Windows 8.1 pops up unwarranted "Out of Memory" warnings while playing full-screen games.

To sum up what I collected from this and other forums in the net, the likely cause for the on-topic misbehavior is a bug in DirectX 11.2 which is exclusively available to Windows 8.1. The routines for scaling the display from game resolution to the monitor's native resolution gobble up memory and fail to release it while the game screen is displayed. The bug does not show in Windows 8 nor Windows 7.

No fiddling around with Windows' virtual memory settings as Microsoft first level support will invariably suggest will fix the issue. [Sorry guys, you respond to trigger keywords you find in the problem reports with template answers from your support manual without really comprehending the issue. Sometimes that is sufficient, in this case its not.]

When the dreaded Windows whine dialog pops up eventually, the desktop screen is shown (which happens to be at native resolution) and the extraneous allocated memory is released immediately - this is why it looks like the error is unwarranted. People that monitored and recorded memory usage while the game screen is in front may confirm the memory leak and the sudden release when the dialog shows. If you are lucky, you can continue to play; if not, the game (or worse: Windows) crashes.

However, even the desktop screen can provoke the bug if scaling is involved (browsers!).

I do not get the error when I set the game resolution to the native resolution of my monitor, effectively bypassing the need for scaling. For users of e.g. laptops with slow graphics this is not an option, most current 3D games start to feel like slide shows at full HD.

Rolling back to ancient graphics drivers sometimes helps, if the DirectX features in question are unused. This takes a lot of experimenting and may result in other unwanted features due to the less mature state of the outdated drivers. You need to find a driver that works with Windows 8 but does not yet implement certain DX11.2 features - note, the hardware vendors receive API documentation way before the public has access and start implementing before the new components are actually available.

Note also, its not really the fault of the driver, its a Microsoft Windows component that fails to work up to expectations.

With Windows 10 and incidentally, DirectX 12 in the queue, Microsoft is unlikely to fix Windows 8.1 / DX 11.2 problems at top priority.

I'd recommend to set up a dual boot system with Windows 8.1 for every day use (I am actually comfortable with the interface) and Windows 7 for gaming. You'll sacrifice roughly 20 GB of HD space and have some discomfort for rebooting now and then but imagine what wonders it can do to your peace of mind...