Question: So my old HDD is from around 2010-2013 and it is very slow and out of space. I purchased a new Toshiba x300 HDD and now I a have a few questions.

1. If I want to move all my files including windows from my old HDD to my new HDD using a drive cloning program are the chances for issues high?

2. Is it worth it to move windows to my new HDD? Comparing my current HDD benchmarks using crystaldiskmark to benchmarks people have posted in reviews show its read/write speeds to be much better.

3. If I don’t clone the old drive to the new one and just use the new drive to put games or programs on will the fact that windows is on the old slow drive bottleneck games or programs that are on the new drive? Will the old drive even come into play when running programs/games on the new drive if all the files are only on the new HDD?

Answer:OK, issues:

Your current drive is “slow”.
Is it the physical drive, or the multi year build up of junk? Likely, both. A migration to the new Toshiba is just moving most of the problem to a new drive.

Win 7 and a 4TB drive as the OS drive. It would need to be GPT partitioned, to access that whole 4TB space. Likely your current drive is MBR.
Strike #2 against migration.

Migration can be great, in the right conditions. Here, conditions are not quite right.
6-7 years between Win 7 installs indicates a new install is likely needed.

What would I do?
Get a 500GB or 1TB SATA III SSD. Samsung 860 EVO or Crucial MX500 would be the default choices.
Clean install of the OS on that. Add the new 4TB and the existing 1TB as second and third drives.

Also, seriously consider moving to Win 10 instead of keeping 7.