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I installed Microsoft Security Essentials on my newly rebuilt laptop.

When I was installing Adobe Acrobat Reader, it also installed McAfee Security Scan Plus - I did not see the option of not installing McAfee.

You shouldn't have multiple anti-virus softwares on the same machine, right? Should I uninstall McAfee?

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Just for info of future readers: When downloading Adobe anything from Adobe's official site, be sure to uncheck "Yes, install McAfee" option before clicking Download. This gives you a smaller download that doesn't have McAfee bundled. – ADTC Aug 26 '12 at 9:36
up vote 7 down vote accepted

McAfee Security Scan Plus is not a pro-active virus scanner, in fact, it's not a virus scanner at al. It merely checks if you have a firewall running, if your virus scanner is up to date and checks several other factors that may lead to your computer being compromised.

So yes, it is safe to keep McAfee Security Scan Plus installed, but if you don't need it, it's safe to uninstall as well.

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It's probably redundant to have though, as Security Essentials covers this functionality I think. – Jeremy Mar 13 '11 at 20:48
@Jeremy true, yet it wouldn't hurt since it only runs on demand anyway! ;) – BloodPhilia Mar 13 '11 at 20:53

Correct, standard practice is to have only one AV application installed at a time, as they are quite capable of perceiving each other as threats and locking up your Internet connection. And yes, you should go ahead and delete it since you didn't want it in the first place!

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The main reason you don't want multiple antivirus programs running at the same time is that they can cause file corruption if they both scan the same file at the same time. I believe that modern scanning engines have improved to the degree that this rarely happens anymore.

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But it's still a waste of resources. And McAfee isn't exactly light on resources – Jeremy Mar 13 '11 at 20:50
It is only a waste if active-scan is enabled on both. Two programs will give coverage that will catch more (no scanning definitions are perfect), but the scanning will have to be scheduled to maximize efficiency. – MaQleod Mar 13 '11 at 20:56

Don't you just hate it when software does that? It's happening more and more nowadays, both as an option (default on) when you download, or as an option (also default on) when you install. (If you download the one with the additional software option on, you don't get the option at install time. Quite sneaky really).

Anyway, if the software works nicely with the operating system it shouldn't cause any problems as such. At the moment I have two anti-virus packages installed - Avast (free) and Sophos (paid). I had been running Avast for ages (and still like it), but had a specific requirement to use Sophos for a job, and just never got round to cleaning them up.

I have not had any problems running the two AV programs at the same time.

The only issue it may cause is a slight slowdown as both systems check the same files.

It's still not a good idea though, and when I have fixed what I broke in Sophos I will be taking Avast off.

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Using two AV programs simultaneously is not recommended and may lead to a small nuclear war between them... – BloodPhilia Mar 13 '11 at 20:33
I'm pretty sure that numerous AV software packages actually recommend against this practice though. And even if you don't experience issues, it's a major waste of resources. – Jeremy Mar 13 '11 at 20:51
Oh, I agree. I just haven't gotten round to uninstalling Avast yet cus I have managed to break the Sophos management console so it's not updating. It's on my todo list. – Majenko Mar 13 '11 at 21:01
Personal Belief: A software that forces you to install something you don't want, is a software that you'd be better off throwing into the trash bin. – Nav Mar 19 '11 at 7:37

When you install an antivirus, it's like installing an OS on top of the existing one.

If you install 2 antivirus, they will fight each other to secure your PC: it will get messy.

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