not 100% sure because i don't use windows often so can't remember but won't the download continue from where it left off, that way you won't need to start downloading from the beginning again, if not then it might be worth looking into trying a different browser that will do this or adding a file download manager that can auto resume a download.
no recommendations for a download manager because i've never used one myself
but i'd install firefox and use that to do the download which i'm pretty sure can and does auto resume a download so you can download a bit every day until you have it downloaded.
in firefox just click on the download arrow and click on show all downloads, a window opens where you can see the ubuntu download which will say cancelled underneath it and to the right you will see a continue arrow, just click on it and then it will continue the download from where it left off i believe.
sorry that was incorrect but did find a way to download a bit every time instead of using a download manager using the firefox web browser, but it's a bit more complicated and involves moving the .part file every time you stop the download and then replacing it again after you later start downloading it again.
full instructions here :- http://www.techsive....wnloads-in.html
so now you should be able to download a bit every day for as long or short a time you want until you have the completed file instead of trying to get it all in 1 long download session.
Edited by terry1966, 13 May 2016 - 08:47 AM.