Windows 8 pagefile on usb FLASH

Not duplicate :)

Windows 8 hides usb flash drives in the list of virtual memory drive list. The picture taken when I installed 2 usb flash drives but they are not in the list. Any body knows the trick to add them here?

You don't need that. Microsoft introduced ReadyBoost with Windows Vista, Windows 7, Windows 8 as a potential way to improve the performance of Windows Virtual Memory.

Ready Boost only improves performance when your USB drive has faster access times then your hard drive does. For most systems, setting a fixed minimum size and no maximum size for virtual memory will provide the best performance.

To make flash drive for ReadyBoost Just take the properties of flash drive and do following,

An paragraph of here: Windows Readyboost purpose , in Jamie Hanrahan answer:

Nor will Windows allow you to create a pagefile on a USB drive. Reason: If Windows needed to read pagefile contents from a USB drive, and someone had pulled the USB drive from its port, there would be no other place to get that data. If it was kernel mode v.a.s. being paged in Windows would have to crash, just as it does on any other attempt to read a kernel page from a failing drive (various bugcheck codes mentioning "kernel inpage error").