Avast Pro automatically uninstalled?

[Behr]

I installed (and registered) Avast Pro on my system (WinNT). Last night, I noticed that something appeared to have automatically shut Avast down. When I attempted to run the program, I get the message, "C:\Program Files\Alwil Software\Avast4\ashAvast.exe is not a valid Win 32 application." At that point I uninstalled the software, reinstalled it, and got the same message. I have since run another Malware program, which removed a Trojan from my system. However I still get the same message when I attempt to run Avast. Any suggestions would be appreciated.

[Tarq57]

That strikes me as quite unusual, since Avast comes with a self-protection system.
Not saying it didn't happen, though.
What I'd be inclined to try, without knowing it will work, is to download the Avast Uninstall Utility http://www.avast.com/eng/avast-uninstall-utility.html, then uninstall again, reboot into safe, run the utility, then reboot to normal and re-install afresh.

As to likely culprits, the only indication is the trojan you reported. Interested in the name of that trojan, and what you used to scan for and remove it. Sometimes additional scanning with a different application is advisable.

[DavidR]

That sounds very like a beagle variant (the not a valid win32 application bit) that disabled AVs it has been able to get round the avast self-defence. It may also come protected by a rootkit.

Also see, anti-rootkit, detection, removal & protection http://www.antirootkit.com/software/index.htm. Try these as they are some of the more efficient and user friendly anti-rootkit tools.
- Panda Rootkit Cleaner - http://research.pandasoftware.com/blogs/images/AntiRootkit.zip.
- Trend Micro RootkitBuster - http://www.trendmicro.com/download/rbuster.asp
- F-Secure Blacklight may not always be available, http://www.f-secure.com/blacklight - Direct link, ftp://ftp.f-secure.com/anti-virus/tools/fsbl.exe

Unfortunately you might just get the same invalid win32 application message.