hah I thought i helped you out with sophos issue. i guess I did not reply correctly on youtube...youtube sucks!lol
anyways, yes sophos does work with out a single problem in windows 8.1 because I am using 8.1 and the extension I use in opera is "AdGuard" its located under "Extensions" and you would click "Get More Extensions"!
If you are not familiar with AdGuard, heres the video:
hmmm I personally stick with free version of adguard because it does an amazing job in blocking pop ups and it blocks phishing sites. I downloaded the trial version of adguard and I uninstalled it because I felt like it was useless to have since free version does a great job. You can watch the video I posted because I show you in that video how many pop ups get blocked.
sorry for that paragraph, just trying to save you some ram usage and installing a program!lol