Hi mchain,
Thanks for your help. Yes, I am still getting the popup, after searching 'avast' in all of my drives, and deleting any folders and files that had it in the name. As far as registry goes, I've only found something mentioning aswrdr and deleted that.
I'm wary of such tools, so I'm not particularly keen on pressing the popup or doing anything with it. Here's a pic that will hopefully give an idea about how this popup looks like on my screen.
Thanks again