If I am adding a harddrive to an already commonly used, already build computer, (Infact it is the one I'm using right now ) I can just put it in and attach it right? No extra work?
You won't be able to use the drive until its partitioned and formatted, you can do all that from within disk management. But yeah, just attach power and data cables and make sure the bios doesn't change the boot order on you.
Only if you are using it as an "extra" drive though. There may also be issues if there is a different operating system on it. I am assuming these are SATA drives, otherwise you will have to check jumper settings if they are IDE HDD,