Victor, I worked with so many people the past 12 years or so and I noticed that in some countries that people that had no money install all the illegal stuff, that still does not make it right, its basically stealing You have to do the math, all the illegal programs and Operating Systems have been altered so that the author can add some garbage to it so he can make some money.
As far as reformatting, I think this would be your best option. Then you would have a nice clean running system with no problems. If you decide to keep things the way they are then I would advise against doing any online transactions with a credit card or doing any online banking, not sure what either Malwarebytes or RogueKiller would have found.
You can go to eBay or Amazon and look for windows 7 64 bit , it will be cheaper than buying win 8 or win 10. The upgrade to win 10 is free from Microsoft for a year and after that you will have to purchase it, I believe you have about 6 months or so left to upgrade.
Take care my friend
Ken