Data transfer - files and setting transfer wizard - questions

I am trying to move from an old computer to a new one at work. I need ALOT of my old files, but hate to transfer ALL of them, 15 years of necessary and unnecessary files, to my new drive. I don't want to clutter up my new drive, but want access to everything. I bought a Terrabyte external drive, thinking I would put everything on it and access it from my new computer to find needed files.

I did not want to spend years finding all the files to save to the drive, so I used the files and settings transfer wizard, which I had never used before.

Problem.

I have a file on my external drive which is holding 50 gigs of info, so I'm guessing everything is there, but it it is not in a format I can access. I am coming to the conclusion it's in a format that would be imported to another computer by the same wizard, at which point I would see the files as they were before.

So.

How can I get all my files, in their accessible format, to my external drive without having to pick up each and every folder and file and transfer it.

Yes, yes, but unfortunately that would be just a small start. The information on this computer has been transferred from computer to computer for at least 15 years, if not 20 or more, different users, same job. There are files everywhere. Alas, I wonder if I will just have to accept fate and manually transfer.