can you stop with taskmaster?
can you rt click avast ball and update>programs?
either way can you open avast and schedule a boot time scan then reboot
send any hits to chest do not delete
if not can you boot into safe mode and run avast from there?
Malware Bytes Anti Malware will get most of this infection
www.malwarebytes.org go to the downloads page
update run check any hits and click FIX CHECKED
you can run in safe mode if necessary (maybe)
while there also run Rogue remover - both free
do you have Spybot or anything similar installed?
if so update and run a scan
spybot can run in safe mode
cleaning your temp fill may make it go away for a while- use internet options if ie or CCleaner ATF cleaner etc
if the above do not work try one of the on line scans first like DR WEB cure it
then do the others