Changing the drive
The placement of the drive in the casing varies from make/model every week almost - so Check that YOU are able to access the drive fefore you go to find the screwdriver. Connerctivity is usually simple.
Copying over the old drive to the new one shouldbe done before you start .
So New drive connected to the machine via an IDE to USB cable[ about £12/20]
But then the trouble starts
The motherboard will detect a new drive.
The O/S will say New computer- don't want to go there unless Microsoft says I can and to do that you have to get online to MS ????????????
Better informed folk may have ideas but to my mind
External drive is the answer for capacity - what is the problem with that?