I copied the dvd when they were offering W10 for free just in case i ever needed it.
If you created the DVD when W10 was free then this would have been an old build of W10 on the DVD.
However you could have download the latest build of W10 "for free" and installed that,
Microsoft make the LATEST W10 code available for anyone to download and install on the following website. So if you do want to install W10 again just download the ISO from here and create the DVD or USB stick with the latest W10 build on it.
https://www.microsoft.com/en-us/software-download/windows10
I have finally got it up & running, but it seemed to take forever. especially the updates.
Microsoft have changed the way they build and download updates between W7 and W10.
In W7 they built updates on top of updates on top of updates, so if you installed an old copy of W7 it could download hundreds of updates to bring you up to date.
However in W10 they now download a complete copy of the latest build of W10 and install that.
They tend to build a new "version" of Windows 10 every 6 months or so. In spring 2018 that created build 1803 and most W10 users have probably got that.
However in late November 2018 they released the "October 2018 W10 update" which was build 1809 (they had a few problems with it when they released it in October so re-released it in November).
They are gradually moving everybody across to 1809 in a phased process.
But of course one of the "problems" with doing a complete replacement of W10 is that it is a large file to download (a few gigabytes) and the actual process for changing from one build of W10 to the other can take maybe 2 hours (depending on the speed of your broadband, the speed of your computer, the amount of data on the PC etc).
BACKUPS - IMPORTANT. Because major updates are a complete replacement of W10 it is even more important that people make regular backups of their personal data and store it on an external hard drive, USB memory stick, or up in the cloud (or all three!).
While I have never had a W10 update go wrong on me they CAN go wrong and you COULD lose all your data.
So to be safe always keep recent backups of your personal data on one or two other media.
Personally I keep VERY LITTLE personal data on my actual computer, I store nearly all my personal data on external hard drives. I can open Word files from the external hard drive, play music from the external hard drive, watch movies from my external hard drive and so on.
The beauty of this is that if my W10 PC crashes for any reason all my personal data is safe.