windows - My laptop starts freezing with mere 2 browsers running simultaneously. ram usage 90+%

I am using a Lenovo G570 RAM: 4GB 1GB graphics. I am running Windows 7 64 bit

I installed a 4 bit RAM and it shows the same!

Recently my laptop starting acting weirdly. It starts to freeze even with some browsers open when I check my RAM meter... it shows 80-96% usage. I tried task manager and killing all the unwanted processes and services running, but that was of no use.

I tried scanning my computer for viruses but nothing showed up on Malware Bytes and Avast.

So, what do I do now to solve this problem other than formatting my hard drive? Is there any solution available?