It sounds like you have, or had, an inferior Antivirus program and your unit most likely needs to be checked out by your local computer repair shop or, if you don't have the $$$ then there are a few programs I would run to verify the integrity of the unit.
ASSUMING you can at least boot into Windows, here is a list of suggested programs with the URLs so that you can go directly to the sight:
www.bleepingcomputer.com/download/publisher/xplode/
you will want to click on AdwCleaner. This will look for known rogue programs and will give you a list of all the entries it found and will give you the option to "clean". Once this program is finished running, it will auto-reboot your unit.
www.malwarebytes.orgwww.superantispyware.com
Spybot Search and Destroy 1.6.2(can be found at
www.majorgeeks.com use search engine under the list on the left side).
http://www.tweaking.com/content/page/windows_repair_all_in_one.htmlHINT: most of the above programs come with a free professional trial that you can run for the best results.
You want to make sure you run these programs how I listed them. Also, pay attention to the repair options in Tweaking.AIO to make sure you have all of the options checked that are needed to reset the permissions for your Windows 8.1 OS.
Once the programs have been run and your unit seems to be responding as it was before having these problems, you can uninstall the clean up programs as they can slow your unit down if left on there for any real length of time(longer than the free trial period... usually 14 days). You may need a flash drive if your unit will not connect to the internet or has issues with not wanting to download the programs.
As per a good free Antivirus program, go to
www.bitdefender.com and scroll down to the bottom of the page and look for a list on the bottom right that says "Free Antivirus Program" and download the installer. YOU MUST make sure any old or expired Antivirus is removed prior to running the install for Bitdefender.
To do this simply go to your Control Panel > Programs and Features> find the current Antivirus program and click it once to highlight it and then click uninstall from the above menu. Once it has finished removing all of the components it may require a restart. Restart unit and start the installation of Bitdefender Free antivirus. *PLEASE NOTE: Bitdefender starts out at a trial version but, if you register it through Facebook or you a Gmail account, it disables the trial version and becomes a full free version that will stay active as long as it is logged in.
Hope this helps.
If you have any questions or aren't sure how to run any of the programs I suggested, please respond to this post and I will give you a walk-thru that will maximize the efficiency of the scans.
I also recommend a good spyware program:
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