I have Dell XPS-L502X(Early 2011) with Windows 7 Home Premium-64 bit. I already reserved my Windows 10 copy and started an update to it that was 2,712.6 MB and failed after 84%, it took for that 17 hrs as i have 512 kbps net speed. I tried many times to continue that update but it won't progress. I tried Update troubleshooter it gives me an error as "Service Registration is missing and Corrupt" and "Windows Update Error 0x80070057(2015-08-02-T-08_01_52A)" are not fixed. P.S.- I have Windows 7 from my Dell Manufacture which is not a crack version. Please help me to get that most awaited update.
Same thing happened to me (Windows 7 Ultimate 64-bit, desktop computer). I spent the better part of the day trying to upgrade via various methods (Windows Update, Media Creation Tool) with no success.
In the end, I had to clean install Windows 7 and upgrade from that. Went off without a hitch.
So, I would recommend backing up all of your files (should be done regardless), reinstalling your laptop, then trying the upgrade again, Also, since you're on a slow connection, I'd also recommend Microsoft's Media Creation Tool (https://preview.onedrive.com/office365promo/) to download an ISO or USB installation media so you only have to download it once. To upgrade from an ISO or USB, just browse to them and run "Setup."
And after all of that, I would recommend clean installing Windows 10 once you've successfully activated it on your hardware (once your hardware has been registered with Microsoft (this is automatically done when Windows 10 is activated the first time after the upgrade), any Windows 10 clean installs in the future will automatically activate without a key (so just click "skip" whenever prompted for one when installing)), as I've read of problems being caused by remnants of the previous OS.