Hello !
I'm sorry to post my own issue as my very first message on Avast forum, but this is bugging me since three days.
I've read TwinHeadedEagle's post on page 2 stating I have to :
1) download AdwCleaner and install
2) launch a scan, reboot then open the log file
3) post here that log file
4) download GMER and install
5) launch a scan, and post log file (same as above)
6) ..... same with Farbar Recovery Scan Tool
^^ then some of you said this threat could be a false positive.
Now, I don't know what to think, since this is my parent's computer, Win8 home (so I'm unsure the above applications will work fine, and how to remove them after all this - not my computer as I said)
Thanks in advance for giving some lights about this issue.