If you install multiple anti-malware products, will they always fight with each other

I have Avast installed and am also trying out other anti-malware software like SuperAntispyware. What would happen if both software found something wrong with the same file, at the same time? Would they fight with each other and get caught in a loop? In the past, I've always just run Avast, and used Spybot and Windows Defender for on-demand scans.

Recently I tried installing Ad-aware after enabling all protection in SpywareBlaster. Ad-aware started picking up these blocked domains as malware sites, but they are just blocked domains. In return, since Ad-aware was going crazy, this made Avast go crazy and do the same thing. Avast never had an issue with the blocked domain lists, until installing Ad-aware.

 

Generally speaking one gets into conflicts when two applications doing exactly the same thing are installed: Particularly true for AVs and FWs. But it can also happen in some other instances. Nowadays antispyware programs flag trojans and viruses, although by design the antivirus should spring into action earlier as it controls the system at a deeper level.

I personally used to have a layered defense, not anymore as the more antimalware programs are active the more the chances of something happening in terms of conflict. A good antivirus program + a sandbox/virtualizer seems to me an effective compromise in today's malware landscape.

If you have no problems with Spybot and Windows Defender you certainly don't need Ad-Aware. If you use a sandbox and/or virtualizer (Sandboxie and/or Returnil for example, they have free versions ), you won't need any antispyware ever in the future (you can have them on demand to check your system every now and again).

 

My personal experience in cleaning infected computers is that they both compliment each other in eradicating same flagged nasties but ofc each combo,situation could be different

 

Certain applications have a good reputation for "getting along". Both Avast and Superantispyware fall into that category. There are several others with a reputation for playing well together.
From my reading and a bit of hands on, the ones that are problem free include (but are not limited to) Avira, Avast, Spybot, Asquared, SAS, MBAM.
AdAware does not have that reputation. Nor, for example, do most Norton products. Indeed, some will command you to remove, say, Spybot when installing.
Generally the larger or more comprehensive a suite is, the more likely to encounter problems with other 3rd party apps.
Rule of thumb has been 1 (and only 1) AV, 1 (and only 1) resident AS, 1 (and only 1) Firewall. As many demand scanners as you want. More than one AS might "play ok" together, but which combos do, and which might not, and under what circumstances, I don't know.