To use your Pen drive as RAM, You have to make Sure that you have a Pen drive which have a Free Storage Capacity of 4 GB. A 8GB pendrive is Highly Recommended to perform this Task
Insert your 4GB or 8GB Pendrive.
Take a Backup of any data already present in your pend rive, Because its advisable to format your pen drive before moving forward.
Now go to My Computers and Right Click on your Pen drive to Select Properties.
Click on Use this Device, Select the number of MB’s you want to use out of total space, Then Click on Apply.
Next you will see Readyboost is Configuring your Cache, When its Done, Just reboot your PC to Feel the Difference
TIP: Once you Start using ReadyBoost Feature, you will have to Practice to Remove your Pen drive Safely Before Ejecting it to Avoid any trouble.
This was a Very simple and Effective Step by Step Guide on How to Use Pen drive as RAM in Windows PC.