OK, go here:
http://www.avast.com/eng/download/programs/avast_uninstall_util.htmlDownload AVClear.exe uninstall utility and follow instructions...
I'm sorry you found this program not-useful. This AV is the best of the best, as well as technical support you will ever find. Free product with completely free phone, mail and phone support. Skinable application, and best of all, it keeps you 100% protected from outside pests. Program updates are very often, but best of all is how often you'll see iAvs updates... sometimes even twice a day...
...but, free country, of course it's your choice... most likely your loss...

Take care
Cheers !