Place-Keeping file on large drive to allow older programs to work

[Frog]

Okay, here's the deal.
Back in November of 2013, I posted here about a problem of a 1.5 Terabyte drive not allowing older programs to even initialize installation.
Some kind soul here apparently told me how to solve this by taking up some space with another file, that then fools the problem programs into thinking they are going on a drive smaller than that.
I even, at the time, played around with changing the size of this file.
So now, I am thinking of cloning everything else on that drive to the ssd I just took out of my main machine.
I am. however, hesitant to delete the 585 gb file without remembering how I put it there in the first place, in case I need to use that trick again.
Heck, back then, I even played around with different size files.
For that matter, if I could remember how to access it, I could even adjust the size way down rather than delete it, just in case.
So what did I do? What do I do?

[UltraSeps]

Have you thought of partitioning the larger drive into 2 or 3 drives?  That'll solve the issue.  Such as D: E: F: etc., whatever.  Once the TB threshold is crossed, it causes issues with some old software and many older systems itself can't access it as well.

[Frog]

My problem is not making it work. This file did the trick back in November of '13.
My concern is that I now want to clone that drive to my now spare 120 gig SSD.
Easy peasy if I am willing to delete the file, but I am hesitant to do that in case trouble arises.

I am just trying to find out
1. What this file is (called FOO, I think, but nothing I can open with a click. It was probably something in the command line when I did install it.)
2. Where it is, so that, if needed, I can just adjust its size to fit on the new drive when I do the cloning and data migration. At the time, I just typed in any size I wanted.

As for partitioning, a drive in operation, years ago, I had Partition Magic on a floppy that did just this.
How are the freebies, Paragon Partition Manager, and EASEUS Partition Master, or others?