Free Anti-vrus

Trollburger

I also would not pay for an AV.

I get Kapsersky as part of my bank account, but if I didn't I'd use Avira / MSE

Anthonis

Firstly everyone should realize the difference between paid AV and free one.
Free one is usually only real-time scanning with some functions.
Paid one (depends on version) has all features to protect totally pc.

There must be only one antivirus on machine!
Now why: having more than one AV reduces pc performance or totally makes it unusable. Also due to high demand it increases pc temperature and power usage. Hard drive is accessed on more higher demand, this also reduces life time of hard drive.

People say from they experience that some of AV are slower some of them are faster.
Well yes, but mainly it all depends on what specification hardware you have.
Also it all depends what features AV has. More of that if you don't need those features usually you can turn them off to gain more performance.

You know only about performance. But I tried specially break the system. I tried various viruses on virtual systems.
And I can say:
Avira is not bad, but passes thru some.
MSE (Microsoft Security Essentials) is best as free AV. Properly configured it also runs great on xp. MSE likely was started from WD (windows defender).
It has almost all basic features that you need to protect pc. It had some issues when cpu was used up to 50%, but I think that one is fixed long time ago.

Now about paid AV: this one depends on your needs. You can find lots of reviews online, forums, blogs, but you have to know what you need.
I personally use Bitdefender Total Security 2011.
I used bitdefender about 7 years on systems and never had issue.
I have lots of features on in so I don't need to install any other software.
It has extended: Antivirus, Anti Spam, Firewall, Parental Control, Privacy Control, Vulnerability, Backup, Encryption, Tune-up, Game/Laptop Mode.
Now you see from 1 application that I don't need to install 10 of them......

People also say oh "install antivirus and some antispyware soft or firewall". Well no, thats already 2 or 3 applications, which may have up to 3 processes running each!
I say: if you need such things, then get all in one software AV!