When you do the upgrade from windows 8 to 8.1 there are a few things to be aware of, I detailed them at the following links in response to other posters also wanting to upgrade windows 8 to 8.1. http://www.bleepingcomputer.com/forums/t/587963/windows-8-service-pack-support-end-date-jan-12-2016/#entry3800696
Point 2 in my post is relevant to youhttp://www.bleepingcomputer.com/forums/t/589753/why-is-windows-81-upgrade-not-applicable/#entry3814077
This was for someone struggling to perform the upgrade, but some of the points in my post may help you, especially the warning about system images.
My own experiences with upgrading, which I did a few months back are documented here http://www.bleepingcomputer.com/forums/t/551980/the-windows-updates-monitoring-thread/page-7#entry3773769
. Post #92 and 93 are somewhat relevant(they describe problems which CAN occur, not necessarily problems YOU will face), however they deal with the problems I had, you might well not experience the same problems. If you do have problems, of ANY KIND, I STRONGLY advise you ask for help and DO NOT immediately replicate what I did, ask before taking ANY of the measures I describe, I only had to take them because of some problems I had, you might not have to worry at all.
Although I had problems as described here I still suggest that upgrading windows 8 to 8.1, as long as the hardware is compatible, is a good idea, primarily because windows 8.1 gets supported for longer, support for 8 ends in january. I advise doing it when you know you will have 3 or 4 days clear, do it on the first of those days and then you have 2 or 3 more days afterwards to fix any issues that might occur. Don't do it on days when you know you'll need your computer the next day, don't do it at a time when you have things that must be done the next day. The download time varies depending on your bandwidth, the install takes a few hours. If you do have problems don't go editing things and altering things(because if done even slightly wrong this could destroy systems if the user doesn't have some system images (made with windows 8.1 after upgrade) to hand), post here and describe your issues, if any occur, you might be lucky, they might not.
P.S. as further advice, if you have any system images at present you might want to restore to them before upgrading, that way you get to perform the upgrade on a "cleaner"* system.
*cleaner as in closer to be brand new installed out of the box. Upgrades like this are ideally done on systems which are in brand new condition or atleast are in close to new condition.
Edited by rp88, 16 September 2015 - 01:46 PM.
Back on this site, for a while anyway, been so busy the last year.
My systems:2 laptops, intel i3 processors, windows 8.1 installed on the hard-drive and linux mint 17.3 MATE installed to USB