You can use more than one on-demand anti-virus at a time, but you cannot use more than active protection anti-virus. Having more than one that stays active in memory will cause system instability.
There are tons of good free ones out there....I've just highlighted a few of the most used. I'm pretty sure all of those I listed can be upgraded to full version, too. I have a paid Anti-virus right now, but it's currently broken (failed update of pattern files apparently disables scanning entirely....I'm keeping safe by running MBAM and SUPER). I'm going to pay for the Full version of Malwarebytes soon (you get active protection, automatic updates, and automatic scanning).
To answer your question, I say "No", those are not worth paying for. Kapersky is a good paid one, I know. Google "best anti-virus" and look for a website with good reviews and a list of the best out there. That is a good place to start looking.
Wildabeast, I do not recommend just using Microsoft Security Essentials. If I recall correctly, using it is NOT a replacement for an anti-virus. It is a supplement. You say you think it is good because Microsoft people know more about Windows than anybody. If they knew so much, Windows would not be so vulnerable to viruses. I say using third party software like MBAM, SUPER, AVG, Kapersky, Avira, etc....is the better choice. You can use it, but I don't recommend by itself. I never used Windows Defender because it never found a darn thing, while third-party software dug the malware out of the woodwork of our old computer. I'll take a look at MSE, but I probably won't use it.
That's my 2 cents.
Edited by keyboardNinja, 26 December 2009 - 06:35 PM.