We need more information from you to answer your question.
1. What version of Avast did you install?
2. What product of Avast did you install? Free, Pro, AIS?
3. What other security software do you currently have or did you have in the past on this machine including:
- Antivirus (AV)
- Firewall (FW) ---- What firewall do you have?
- Trial versions of AV, FW and other security programs
- Other security software
- If they were in the past, how did you remove them (the vendor's uninstaller's tool or another way)?
Is Avast working fine otherwise? Is it updating normally? Is your machine working fine otherwise?