after second 3rd party scan, "fake" windows security alerts window pops up and says Avast is not turned on, while Avast itself says it is secure. I say fake becuase I think the real window says "windows security center", not alerts.
As I can not see none of the rogue program, this is a legitimate and Windows related.

Run this FRST script. If the problem still persists after this FRSTFix, that isn’t malware related as you do not have any active malware.

1. Open notepad and copy/paste the text present inside the code box below.
To do this highlight the contents of the box and right click on it. Paste this into the open notepad.
NOTICE: This script was written specifically for this user, for use on that particular machine. Running this on another machine may cause damage to the operating system


START
HKCU\...\InprocServer32: [Default-pngfilt]  <==== ATTENTION!
U5 AppMgmt; C:\Windows\system32\svchost.exe [21504 2008-01-19] (Microsoft Corporation)
END

2. Save notepad as fixlist.txt to your Desktop.
NOTE: => It’s important that both files, FRST and fixlist.txt are in the same location or the fix will not work.

3. Run FRST/FRST64 and press the Fix button just once and wait.
If the tool needed a restart please make sure you let the system to restart normally and let the tool completes its run after restart.

The tool will make a log on the Desktop (Fixlog.txt). Please attach it to your reply.
Note: If the tool warned you about the outdated version please download and run the updated version.