Download Kaspersky Antivirus or eset NOD32 antivirus. Then download Spybot Search and Destroy, Windows Defender and Spyware Blaster
Make sure Spyware Blaster is updated. Also download Comodo BOClean
First, delete Avast. It is too wimpy. Then install free trial of Kaspersky AntiVirus or ESET NOD32 antivirus. Make them do Full Computer Scan of any viruses or rootkit. then use Windows Defender to do a Quick Scan of the system. Update Spyware Blaster to a scan. Delete anything those programs scan. Then after installing Comodo BOClean, Reboot the system. Then do a scan. Delete anything the program scans. That should help the system.