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Do I Need to Deactivate My Old Anti-virus Before Installing the New One?


Hey, Leo. When I bought this computer, Norton anti-virus came with it. Norton anti-virus is about to expire and I don’t plan to renew it as I’ll switch to Windows Defender since it’s recommended by you and by others. My question: can I activate Windows Defender before Norton anti-virus expires or do I need to uninstall Norton first? Also, should I uninstall Norton after Windows Defender is installed? Finally, how do I activate Windows Defender? I’m running Windows 7, X64, on an HP desktop.

A note on product names: for Windows 7 what you’re really talking about is Microsoft Security Essentials. That’s the old name for “Windows Defender”, which is what you would use if you were running Windows 8. However, for Windows 7 and before, what we’re really talking about here is “Microsoft Security Essentials”.

Typically, the answer to your question is “yes”; you should uninstall the old anti-virus software before installing the new.

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Avoiding conflict

Remember that multiple anti-virus programs can, in fact, come into conflict with each other when they’re installed together.

I recently saw this on a friend’s computer. Basically, his first anti-virus had expired, and he installed another without removing the first. After that, the computer was slow doing just about anything. We also suspected that the problem was causing emails to be lost or incorrectly funneled to spam, or deleted.

The right approach is to uninstall the old, and then install the new. However, this statement assumes that you are handling this in the safest possible way.

Safety through the transition

First, you have to have a firewall in place. Technically, without anti-virus for even a few minutes, you’re somewhat more vulnerable to attack or infection.

It’s probably enough to be behind a router, which acts as a hardware firewall protecting you from the internet. However, if the other machines on your local network aren’t necessarily trustworthy, (i.e., they’re the kids’ machines, or someone you know has bad surfing habits) then you probably want to have your Windows firewall turned on, if it isn’t already, before you uninstall your old anti-virus.

The second assumption is that you actually don’t do anything else between the uninstall and the install. Again, technically, without an anti-virus installed even for a few minutes, you’re somewhat more vulnerable. If you get distracted between the uninstall and the install and you go off and surf the internet, you’re basically vulnerable to whatever you happen to download.

As long as you make sure you do the uninstall followed pretty much immediately by the install while having a firewall in place, you should be okay.

Activation? No need

As for activating Windows Defender/Microsoft Security Essentials, you don’t need to. There is no activation. Once you have it installed, it will start running and it will start doing its job.

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16 comments on “Do I Need to Deactivate My Old Anti-virus Before Installing the New One?”

  1. If you are worried about being unprotected during the time you’ve uninstalled one virus and installing another, you can unplug your network cable or turn off your wireless during the installation. It’s not perfect as you probably won’t have the latest virus definitions, but it will give you a little more protection during the switch. I personally don’t bother with that any more as I trust my Windows and NAT firewalls will protect me from local network and online attacks.

  2. What I would like to know is, if your computer is Windows 8.1 and it comes with Windows Defender on it, do you have to remove Windows Defender in order to install Norton? I have a friend who just bought a computer with Windows 8.1 and we installed Norton on it. It came with McAfee on it as well and we uninstalled that first, but now I’m concerned about the Windows Defender. I thought you were just supposed to turn it off somehow. If so, how do you turn it off? What do you do in this situation?

    • In most cases 3rd party tools like Norton will automatically turn off Defender as part of their install. If there’s no complaint at install time I would not worry about it.

  3. I bought a computer with Windows 8.1 and it came with McAfee know the firewall is off so I want to know what do I do to make it on,

  4. Hi Leo, I’m just learning how to navigate this new laptop. I was a Mtg. broker for years and only used one program on the computer, Calix. for work. Then the computer came with one on it already. This new laptop had a trial version of Mcaffee on it. Now it’s telling me that the trial is over and I don’t want to buy a software program. I need to know how I remove the McAffee and the how I install the windows defender. I have a router through my cable co for the computer and someone told me that it will also serve as a firewall but it wouldn’t hurt to turn on the windows firewall either. Do you recommend the windows or should I download a free version of something else. I”m fearful and confused. Thanks, Jamie

    • You should be able to remove McAffee in Programs and Features in the Control Panel. As for installing Defender, it depends on which OS you are using. What MS has available for Windows 7 and older is Microsoft Security Essentials which available on their website. If you are using Windows 8.x, uninstalling McAffee should cause Windows to either automatically enable Windows Defender or ask you if you want to enable it.

    • If this is Windows 8 then Defender is already there. You can uninstall MacAffee in control panel -> Programs. Doesn’t hurt to turn on Windows firewall at all, and I don’t think another is needed in normal use.

  5. Hi Leo,
    I have Windows 7 and I have two anti-virus programs installed on my computer. I would like to disable one and make the other my main program to use but whenever i try turning the other one on it doesn’t work. I tried everything but still no luck. Can you please help me?

    • You’re lucky then. Someone claimed to be a tech and told me I can have 2 anti virus programs. I did it and my computer froze and wouldn’t boot. It cost me $129 to fix it.

  6. Leo, I purchased a new laptop and anti-virus program Total Defense was on it…it’s time now to purchase another round of TD or I was thinking of installing Total AV..the free version. Do you recommend Total AV? With the new machine Microsoft 10 is on it. And do I need to uninstall Total Defense first? Thanks! Jean


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