The common belief is that the more ram installed, the faster the PC you get, this is not always the case. What more RAM does is that it makes it possible to open more applications simultaneously. It switches back and forth between these opened applications at a faster rate than you could on the previous RAM, hence more RAM equals better multitasking abilities.
You have to be aware that having a 32 bit system will limit your ram to around 4GB no matter how much ram you have installed, Using a 64 bit system changes things yo can utilise as much ram as your motherboard will allow.
How much Ram do i need?
Windows will run on 4GB of ram though i think 8GB of ram is much better, you can run all your basic tasks with this, EG you can happily edit your word document, while running youtube and downloading some files (Multitasking) with ease.
Though if your gaming most people prefer to use 16GB of ram bear in mind you will need 3GB of ram (approx to run windows) See below pics of windows 7/10 in steady state Ram usage.
Windows 7
Windows 10
As you can see on my system iam running with 32GB of ram i have a dual boot system running windows 7/10 this is more than enough for me i rarely exceed over 10GB of ram unless iam running a VM (Virtual machine)
I would say for basic computing and light gaming 8GB is fine, If your a serious gamer i would suggest 16GB, If you do a lot of rendering, working heavily with graphics and video i would suggest 24/32GB of ram
But always check your motherboard to see how much ram you can install you can always download the scanner at Crucial US | DRAM, Solid State Drive (SSD) & Memory Upgrades that will tell you how much ram you can install and choose the correct ram for your system.
