If I add hard drive will it increase my memory?

No. Another HD will increase storage space.

What is the problem you are trying to solve?

RICKJ is right.

Adding another hard drive will increase storage space.

If you want to increase your memory, you will need to add more RAM. That is if your motherboard has a slot available.

Just to clarify... many people confuse memory and storage space. They are measured the same way (In Bytes, KB, MB or GB). They are used similarly (to store info). However, Memory usually refers to RAM, what I call working memory. This is space that holds what you are currently working on. When your PC is shut off this space is emptied. Your Hard Drive is storage space. Data is stored on it and then retrieved into RAM to be worked on.