I run Win '98, and that suffers from a gradual decrease in memory over a period of time, it does not arrange it's memory very efficiently, (a common fault with Win '98...).
Over the course of a day my memory can decrease from 768 MB to nearly zero. This slows everything down...and in the end I get the message...."not enough memory to run the application".
This requires a re-boot to restore the memory back to normal.
Cheers...!
Paul....also suffering from loss of brain memory...need a "re-boot"...

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Note: small children equipped with glasses of Coka Cola dripping over the computer and keyboard can also affect it's efficiency...

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Win 8.1 64-bit. DX11. Advent Tower. Intel i7-3770 3.9 GHz 8-core. 8 GB System RAM. AMD Radeon HD 7700 1GB RAM. DVD ROM. 2 Terra Byte SATA Hard Drive. Philips 17" LCD Monitor. Saitek Cyborg X Fly-5 Joystick. ...and a Briggs and Stratton Petrol Lawn Mower.