help

how cleane this Win32:DNSChanger-ZZ [Trj]

Did avast detect it but not able to remove it ?

Try avast boot scan…

If you have avast 4.8
Boot time Avast Antivirus Scanning http://www.digitalred.com/avast-boot-time.php

if you have avast 5
http://sites.google.com/site/spg20scottsweb/home/avast-5-boot-time-scan

Check your computer for Malware with

Malwarebytes Antimalware http://filehippo.com/download_malwarebytes_anti_malware/
after install click UPDATE and run quick scan, click on REMOVE SELECTED to quarantine anything found

SUPERAntiSpyware http://filehippo.com/download_superantispyware/
Are cookies really spyware and are they dangerous?
http://www.superantispyware.com/supportfaqdisplay.html?faq=26

If anything is found come back and post the scan logs here