Replace Or Add Hd To An Older Computer

Hi,
I have a computer that is few years old. The HD crashed and someone that helped me at the time installed a new 500G drive with Windows 10.
The computer works fine but since this is the computer that I use to save all of the family pics and videos it is not enough.
I need an additional internal HD. The computer is used mostly for that and for some gaming but not too heavy graphically.
I want to buy a new 3T HD, but wondering if I should:
1. Replace the current HD with it (which will require to re-install the OS)
2. Add it as an additional HD (do I need to do anything other than the hardware connections?)

What should I consider when looking to buy new HD? and which of the above options is better

 

2. Add it as an additional HDD. I recommend SSD for Windows "HDD".

There are not much choices for 3TB drive as about only manufacturers are Western Digital and Seagate. You can argue forever about which one is better.

 

So to keep the OS on the existing (non SDD) HD, or are you suggest to buy one SDD and one HDD ?

 

I suggest buying SSD for OS. And in case you buy 3TB HDD and SSD, then you probably have no use for 500GB one.