I had all the builds back to 98xx or 99XX, but all those pre-TP1 builds were on discs. I think I might have thrown them away, since I had burned them myself. I mad that decision when I finally figured out that I had a digital entitlement license attached to my Micro$oft account.
In addition, I had .ISOs of all the subsequent builds, but after I came back in August to grab the updated ESD2ISO tool from @Kari's tutorial, having realized that anything I had made since around AU was useless (which I figured out the hard way, trying to get the most recent IP build to boot in August lol), I made the decision to get rid of the entire store of .ISOs (>250 GB!), seeing as I would never use any of the previous IP builds again. So, I deleted all of them.
I then used HeiDoc's ISO down loader utility to grab the major releases, plus IP build 14965, and I did use the updated ESD2ISO tool to make an .ISO of 14971, but my storage drive is still 200 GB lighter