Converting 8k textures to lower freeze

Whenever I try to apply a 8k texture, or add something that contains a 8k texture to my level, I run out of ram. My system’s ram usage goes to 99%, and at that point, the whole system freezes. Can’t move mouse, click, use keyboard, anything. I have to shut it down with the power button. As a solution, I have tried to convert all 8k textures from the Open World Demo to lower resolutions, as here:

But to export the 8k textures, Unreal has to load them, and whenever it tries to load them, the PC freezes. I have let it there for hour, but it is just frozen. It can load 4k and lower resolution textures, but not 8k. So, can someone maybe provide a download link for the lower resolution textures of Open World Demo, or can I somehow convert them myself without running out of ram?

My specs:
Intel Core 2 Quad Q6600
MSI Nvidia Geforce GT 640 OC (2gb)
4Gb DDR2-667
500Gb HDD
Windows 10Pro Insider Preview 64bit

I having exactly the same problem. My pc shows 100% ram usage and the whole system freezes. I cant even shut down my computer or make the editor crash!

Sorry for the grammatical error in the first sentence.