(assuming you have Windows)
There should be no difference between a fully reformatted drive and a new one (other than wear and tear ofc) as a format erases all data. So it's your browsing habits & lack of adequate security that is prolly the problem... but no worries, it's easy to fix for free.
As you should NEVER run multiple anti-virals, uninstall ALL security software completely. As some... less than scrupulous software manufacturers don't include an uninstall option and sometimes even your OS fails at removing unwanted programs, you may need a utility program to help with this.
TuneUp Utilities is an excellent choice for this, even though it's a trial version (expires) it offers full functionality and unlike some other variants, it won't harm your computer even with it's automatic settings. It's "One Click" maintenance does a pretty good job as well.
Antiviral software is much like any other product, you don't necessarily get what you pay for (particularly true if you don't pay for it lol) and just because it's popular doesn't mean it works well - Norton & McAfee are both the most common and they BOTH are amongst the
worst. Not only do they not provide adequate security - they both use "false flag" tactics, alerting a threat that doesn't exist to promote their software, with the theory that if you see more alerts - you'll think it must be better than the competition.
If you wish to pay for some of the best protection,
ESET Antivirus is without a doubt some of the most respected security software available, it also has low resource demands so it won't bog down your system. If you don't wish to pay for a subscription,
avast! Free Antivirus is an excellent, easy to use & comprehensive security suite. You'll only need to "register" it by submitting an email address - that doesn't even need be your own. A tip though - it's sponsored by Google and it'll want you to install various Google accessories, don't do it - just uncheck those options, it's unneeded bloatware.
The best protection is prevention, Windows Internet Explorer is riddled with security vulnerabilities and allows no real customization options -
Mozilla Firefox is simply a far better browser for many reasons, one of which is it's customization via "plug-ins" and while you don't want to bog down your browser with too many (around 6 - 10 plug-ins, depending on what they are), the following are critical for secure browsing and have the added benefit of providing an ad-free internet experience;
Adblock Plus:
https://addons.mozilla.org/en-US/firefox/addon/1865/ works by "blacklists" of known spammer/advertisers - as the name would imply, it "blocks" the majority of annoying & potentially dangerous advertisements. After install you'll see a small "stop sign" in the top right hand corner of Firefox, should you ever wish to allow an ad or block one that got through - right click it for options.
NoScript:
https://addons.mozilla.org/en-US/firefox/addon/722/ - blocks all scripts, plug-ins, and other codes that could be used to attack your system, somewhat awkward at first you'll need to go to the bottom right hand corner of Firefox and right click the NoScript icon to allow trusted sites, but after a bit of use it's far less intrusive as it "remembers" your settings. As "scripts" are the MOST common source of malware - it's critical to prevent unauthorized scripts and Internet Explorer simply doesn't let you do that.
Using the above - I've had my home systems up and running, connected to the internet and active 24hrs a day for over three years with
no issues, so I hope this helps
