You Might Have A Rootkit, A REALLY Bad Rootkit.

Now Lets See If This Works…

Open The Avast Interface.
Click Scan.
Click Boot-Time Scan.
Schedule A Boot-Time Scan (Make Sure In Settings It Checks: All Harddisks, System Drive And Auto-Start Programs (All Users).

Optionally, You Can Change The Sensitivity To Full Where You Will Possibly Get More Results But Some May Be False Positives (Anyway, I Have Mine On Full.)

So Good Luck!