Can Avast! Pro co-exist with MS Security Essentials?
Also, is there a simple way to temporarily turn OFF Avast (as there is with MSSE)?
No.
Please uninstall MSE…!!
It does not need to be uninstalled. All that needs to be done is to turn off “Realtime Protection”. Please give correct advice!
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I did.
You can turn off Avast by right clicking on it’s system tray icon and mousing over “avast! shields control” and then choosing a period to disable them all for.
NO! disabling realtime protection only is INSUFFICIENTas it could still possibly leave low level drivers of MSE running.
these drivers could STILL conflict with Avast! drivers, causing potential problems like freezes or BSOD.
please uninstall MSE
No sir, you did not. You gave the member the impression the only option was to uninstall the product and that is not correct. The product can remain installed as long as the “Realtime Protection” is turned off.
Where is the Microsoft documentation to support your claim?
Sorry, but you’re wrong.
Documentation is all over the internet if you do a search and is widely common knowledge, you do not install two antiviruses on the same system, disabled or not.
Use the Windows Services GUI to disable MSE or far better just uninstall it. 
You might get away with it being disabled in that mannor for a while but there is still the chance of avast detecting it, much safer with it removed completely.
Right here (step 3) → http://experts.windows.com/w/experts_wiki/89.aspx
Maybe you should do your homework before accusing someone of giving incorrect advice.
@Charyb: thx for the link, remembered reading it somewhere but did not bookmarked it.
Every reference on that site indicates “real-time”. Here’s what is indicated regarding on-demand.
However, you can have an on-demand scanner, such as Malwarebytes, installed. Malwarebytes offers two different scanners – one on-demand (free), and one real-time (paid). The on-demand scanner does not conflict with MSE’s real-time scanning.
Now, when one disables real-time MSE the only tool remaining is an on-demand tool.
I do admit, though, the OP didn’t specifically indicate what OS is being used and that page states XP is handled differently than Vista and Windows 7.
As already mentioned by AntiVirusASeT that even with being disabled there are still low level active drivers that may conflict so as advised dont install two AV’s, dont know why your arguing this as your not going to win :
If you had read the thread correctly
Quote
Not only should you remove your current anti-malware product(s), you should also uninstall any free or trial anti-malware products that may have been installed on your PC when purchased, even if never activated.
Winning!? What are you on about!?
It is clearly written that it is two real-time scanning tools that is the problem. And it is also clearly written that one on-demand and one real-time scanning tool is not a problem.
Now that page was provided as being the page to go to for the information needed and that is what is written.
You think it’s an accident that there is a very clear distinction between the “real-time” and 'on-demand" tool in every reference to a scanning tool?
The on demand tools they are suggesting can be used are programs such as Malwarebytes and Malwarebytes isnt an AV
You are always free to try having 2 installed AVs. Active or not.
You are free to try other things also, like; try out for the Olympics…swim the breadth of the English Chanel…climb Mount Everest…or if you just want to stick to computing, running a sandbox inside a virtual machine that is running in a sandbox.
All these things you are free to try. Some will even rise to the challenge and succeed. But for most people, “free to try” ends up meaning “free to fail”.
The real challenge seems to be finding a resident AV that will shut off all real-time features, and stay off through all times it is installed. They are not made with this in mind.
Another Quote from the same link since you cant seem to find the correct reading material
Can I have more than one real-time anti-malware product installed?
No. Having more than one real-time anti-malware product installed will compete with other anti-malware product(s), and can cause severe performance problems and system instability issues, and may limit the effectiveness of the products installed. Even if you attempt to have more than one product installed, with one active and another disabled, the disabled product will likely still have active components and/or drivers installed that will conflict with MSE. The important issue here is that any other product with real-time scanning will conflict with MSE (or any other real-time product).