Hey Shobha,

Try using this removal tool: https://www.avast.com/uninstall-utility

If that doesn't do the trick let me know and I'll walk you through a manual search and removal process.

Cheers... Jim

What is issuing that message, where is it coming from? Can you post a screenshot of the message?

avastclear.exe is portable, it doesn't need installing, just run the downloaded file and follow the prompts.

Not silly questions at all, just need a bit more information.