Attach here screenshot avast message.

Download TDSSKiller and save it to your desktop

Execute [b]TDSSKiller.exe[/b] by doubleclicking on it.

[*] Press Start Scan

[*] If Suspicious object is detected, the default action will be Skip, click on Continue.
[*] If Malicious objects are found, select Cure.

Once complete, a log will be produced at the root drive which is typically C:\ ,for example, [b]C:\TDSSKiller.<version_date_time>log.txt[/b]

Please post the contents of that log in your next reply.