Does it matter which order I put my files back into the new drive for the absolute best performance. Do I go install all the games first or do I put all my animes and videos on the drive first? And also, I never used to disk defragment on my old drive. How often should I do this for the new drive?
If I copy a whole bunch of videos at the same time, will the videos be fragmented?
It makes no appreciable difference in what order you copy data or install software.
On a new hard drive, if you copy across all your videos en masse, they will not be fragmented.
Defragmenting: install a third-party defragmenter such as the free Smart Defrag.
When you click "Analyse" it will tell you if the drive needs defragmenting, otherwise it will just say "No need to defrag".
That's a very useful feature since defragmenting too often or unnecessarily will shorten the life of the hard drive, but that doesn't mean it should never be done at all if it's necessary, otherwise the drive's performance will suffer.