Insert the USB Drive > Now Right click on the USB Drive and Open Properties.
Click the ReadyBoost Tab.
Then click on Use this device then select the correct memory size to use.
Click on the Apply button.
Insert the USB Drive > Now Right click on My Computer (This Computer) and Open Properties.
On the left side on the Properties Window, Click on Advanced system settings.
In the Advance Tab under Performance, click on Settings.
The Performance Option window appears, Click on Advance Tab.
Click on the Change Button under Virtual Memory.
Clear the box of Automatically Manage Paging file size of all drives. Then in the Custom Size field, add your USB Drive size. Now Add the same Value in both boxes and click on the Apply button.
Restart Your system, and now USB Drive works as Virtual RAM.