Just installed, registered AVAST! Home.
Before registering had error message re: subject
First with McAfee Trial & MSSE.
Second withourt McAfee.
OS: Vista HE on Aspire 5536 series.
Query: can I ignore error message.
I decided to try AVAST! because reviews are cornstistenly high & has fast scan time as compared to previous AVG.
Regards, ZN
Since you’ve had various other AV programs on your computer, please follow the directions outlined in the following link.
http://mysharedfiles.no-ip.org/TipsTricksFreeware/How2InstallAvast.html
You should never have more than one Anti Virus program on your system and unfortunately almost all AV’s
leave things bhind when they are simply removed through the Add/Remove function.
If you have any questions, just fire away. We are all here to help you. 
I really can’t understand where the unsupported OS comes from as avast 4.8 supports win9x through to windows 7, but the one thing I do know previous AVs can cause havoc.
So you should uninstall all other AVs prior to installing avast. Even then some leave remnants that can gum up the works.
2007 version - http://download.mcafee.com/products/licensed/cust_support_patches/MCPR.exe
Also see - How do I uninstall SecurityCenter? http://ts.mcafeehelp.com/faq3.asp?docid=71525
Thank you all.
Acer included McAfee Security Center triial-ware. Had to go library wireless to download avast. Home connection too slow. So use the mcafee for awhile. The reports I read said MSE & AVAST works well together. Never used avg on this machine (just on previous).
Will check out the McAfee removers, since just used Control Panel.
If error message re-occurs could take snapshot.
Again thanks all, ZN
There are occasions when MSE will conflict with avast, there are already some cases of this in the forums already. There are some using it in conjunction with the avast beta trial as the beta wasn’t fully functional.
However, the premise about two resident AVs still holds, don’t, it will at some point bite you in the ass. Having two resident scanners installed is not recommended as rather than provide twice the protection it can cause conflicts that could leave you more vulnerable.
Just migrate to new OS - windows 7
I use MSE with Real time protection off set for daily update when I know the system is powered on then do a Quick scan that takes about 5 minutes on this Windows 7 system.
Make sure McAfee is removed like DavidR says.
I would not be hesitent in removing MSE if it caused a problem for me as I much prefer avast! as it has good features.
That is nice to know that you can disable the resident protection, which would hopefully remove any possible conflict.