I want to use both Avast and Avira!!! No offense intended. They both seem to be good software with similar reputations.
Does anyone have any experience of this where they could advise??
Presumably I should only have one on access scanner?? I was going to use Avira because it is easier to switch off the on access scanner in Avast.
Are there problems with keeping other Avast real time shields in place??
Many thanks for your help. 
running 2 AV on the same computer can create all kind of mysterious windows errors and false detections
why you should never run more than one AV ( see reply from quietman7 )
http://www.bleepingcomputer.com/forums/index.php?s=49db784baecf17e7b189c833aafb624d&showtopic=260844&view=findpost&p=1441638
Clash Of The Antivirus Apps
http://www.smartcomputing.com/editorial/article.asp?article=articles/2003/s1407/38s07/38s07.asp
Surely it is the real time scanners that can/might clash and cause a problem??
If I have them both installed but only one is running its real time scanner/shield and I use the other only for on demand scans that cannot be a problem??
What do you think.
Thanks for your help.
If I have them both installed but only one is running its real time scanner/shield and I use the other only for on demand scans that cannot be a problem??it is answered in the first link......
here is a way to do it http://www.surfright.nl/en
Hitman Pro 3 - Second Opinion Malware Scanner http://www.surfright.nl/en/hitmanpro
@ dogdog
It is the low level drivers that hook files so that they can scan the file in the first place. These are still running even if you disable the scanners.
Looking at Process Explorer it would seem that the two running Avast processes are:
Are there any others??
I presume that Avast UI.exe is the Avast User Interface??
And AvastSvc.exe is the sefvice that contains the module for the Real Time Shield and the Scanner??
I can stop AvastUI.exe starting on PC start up via msconfig.
Is there a way to stop AvastSvc.exe starting as PC starts up??
The objective is to have Avast installed but no Avast processes starting automatically with the PC start up. The Avast processes would only start if the user manually starts them. Is there a way to achieve this objective??
If I go to Control Center → Uninstall or change a program and then start the uninstall process for Avast, one of the options is “Change”.
I haven’t yet explored all the options as I did not want to damage the Avast installation. Could someone advise what is possible via this route?? What happens if I remove the ticks fom all the boxes under Shields and proceed to “change”?? Are there other options presented later??
When installing Avast there is a Custom Option. What alternatives does this offer. Can I install the Avast Scanner but not the Avast Shields?? If this is possible and only the Scanner is installed would there be any Avast service started with the PC start up??
Many thanks for any help that you can give me.
@ dogdog
Please read:
Why can’t I use msconfig to change my services?
http://www.blackviper.com/AskBV/XP25.htm
I would follow DavidR and Pondus’ advice as they know avast! in and out.
I like to try things - a learning experience!!!
So any answers to previous post would be gratefully received.
PS: Currently on my PC I have an AV (including real time scanner). I also have installed on my PC: SpybotSD, Norton (free via Google Pack), SuperAntispyware and Spyware Doctor. None of the 4 start on PC startup; I only start them when I want to use them to perform an on demand scan. I have never had any problems with interactions between these 4 programs and my main AV.
My current main AV is from Zone Alarm Security Suite which uses Kapersky as the anti-vitus/anti-spyware engine.
I am in the process of replacing ZASS with Comodo Firewall + Avast/Avira.
As you like to learn thing then stick around.
Those are Processes/Services and aren’t the low level drivers which are loaded by avast and aren’t user configurable. That is the whole point of resident on-access scanners.
In order to scan a file it has to hook/intercept the call to run it so that it can be scanned before it is run and that is what the low level drivers do. Yo are throwing a bone into the dog kennel and two dogs are going to fight for control.
At best this just causes duplication of scanning an increased CPU and RAM use, at worst the drivers could conflict causing a lock up at. This is a pain as it would require a reboot to resolve the lock up, just imaging if this actually happens during boot, you could be locked out of your system until you manage to uninstall one or other AV from safe mode (if you are able to get into safe mode).
What about:
Currently on my PC I have an AV (including real time scanner). I also have installed on my PC: SpybotSD, Norton (free via Google Pack), SuperAntispyware and Spyware Doctor. None of the 4 start on PC startup; I only start them when I want to use them to perform an on demand scan. I have never had any problems with interactions between these 4 programs and my main AV.
Why are these different??
I notice that you are using SuperAntiSpyware with Avast??
How can there be interference between 2 AV’s if one of the AV’s has no real time scanning and is only used for on demand scans??
Surely the hooks/intercepts are only triggered by the real time scanners??
I am grateful for the help.
Grasshopper there is so much to learn about 
SpyBot S&D has become obsolete as it has not kept up with the times and Malwarebytes’ Anti-Malware (MBAM) has surpassed it!
Because anti-spyware applications operate differently and most of them don’t have proactive/resident protection unless you paid for the pro versions.
I somehow doubt the the AVs aren’t running on boot if they are designed to be resident the low level drivers will be loaded early even if you have resident protection disabled.
Norton I probably the worst AV I have come across for leaving remnants behind, which conflicts heavily with whatever you install next, these forums are littered with such topics.
Just because you haven’t had any problem doesn’t mean it won’t bite you in the ass at a point/time of it’s choosing. If that happens at boot as I said you could be locked out of windows normal mode.
dogdog,
If you want to use two av’s, use:
http://www.clamav.net/about/win32/
or
http://www.immunet.com/main/index.html
or
http://www.cloudantivirus.com/en/
with avast! or Avira or ZASS or any other av. ;D
agreed with everyone. if you are using all that at once you are simply asking for trouble… EVEN if running on demand. as many stated they will run low level drivers NO MATTER if you disable them resident wise or not. and YOU CAN NOT DISABLE THOSE just by turning off the procc’s you mentioned above. pick one and run it NOT 2 or 4 of them. you will end up with worse results doing that then if just running one good one at one time.
if you want multiple engines like that get your self hitman pro, otherwise there are a few others that have dual engines as mentioned above add gdata to that list as well and there are even others…
dogdog,
Welcome to the forum.
We have helped many people here because they have had other resident AV’s on their system, or remnants of other resident AV’s thus causing problems. Please listen to the previous posts about having not having more than one resident AV on your machine. Granted, you have been very lucky so far, but how long will your luck last?
My luck lasted about a month, when I first installed Avast! on top of the McAfee that came bundled with my pc.
Seemed logical, turning McAfee off, keeping it for on-demand purposes. But logic is only sound when you see the whole picture, which I did not.
Hindsight came in the form of many BSOD’s.
I wasn’t unlucky enough to get a reboot-loop or anything that nasty, but still unpleasant and potentially damaging.
Save yourself the headache. Layer different forums of protection, not the same.
I agree with layering your security lines of defense. This along with safe browsing practice, common sense, and keeping your software up to date are are few more good practices.
avast has a better update scheme (servers), is much more configurable and could fit the users needs, do not have the stupid annoying popups that Avira insist to give to their users.
avast is very good on infected websites detection (Avira let this only for the paid version) and also for pdf exploits, scripts, etc.
Avira has a good heuristic detection and also file detection is, generally, at higher rates that avast.
Hi, dogdog,
If u want to use two AV then u should use MSE and Avast. they are compatible read here http://blog.avast.com/2009/08/28/greetings-from-redmond/ but i dont think its advisible. There is no point using two AV, instead u can use Avast with MBAM or SAS, as a on demand scaner these two are probably the best out there.