If there is nothing wrong with your old HD and all you want to do is to put a bigger one in for more capacity, you can clone the old drive to the new drive. Cloning is creating a mirror copy of the old one with OS, programs, folders/files in the new one. There is option for you to make the partition larger to make use of the larger capacity.
There are a couple of sticky threads here you can read up. Mostly is related to cloning a SSD but it should be the same for other HD too.
If you run into problem, come back here and I will try to help you.
But if you are on a desktop and you have a spare drive base, you can just add another HD to the system without going thru the trouble.