Hi again, when I start avast to scan my computer I receved this message and my avast did not scan the computer, what might be the problem?Everything else seems to work fine.
Unknown error
The scan complited with error
42000=Unknown error
Could you find the ‘last scanned’ file into the avast logs or on the report?
On the report tab of settings you could check the ‘OK files’ and scan again… The last file will be there, then post the name and the path here. Maybe we can guess a little bit more.
No there is no last scan becouse I install the last version of avast yesterday,I get this message when I click on the icon to start avast, and again when I click to scan the archive files and ect.I gess that only works the resident protection, also when I was scaning with Ad Aware , my avast find two trojan viruses in the computer and deleted them.
Is there any other antivirus in your system?
Can you repair your avast installation through Control Panel?
I uninstall AVG antivirus and deleted what was left from it before installing Avast, then restart the computer and installed Avast, so I dont tink that something was left behind of AVG.
Yes… could be something left behind…
Search Windows Registry for Grisoft and AVG keywords.
Maybe some legacy and service drivers are left behind… 
Ok, thanks, if this dont works I will writte the problem again. 