How to stop notifications

I just downloaded Avast free and I’ve done all the scans it will let me but I can’t get the box to stop popping up. it says its in c:\windows\system32\dllhost.exe and the object is hxtp://26714.t.c.adlinker.net/ I don’t like to mess with dll files. Is this something i can delete? It pops up every couple seconds and blocks 1/4 of my screen. Why wasn’t this taken care of when I did a scan?

Please follow the instructions and attach the requested logs to your next post.
http://forum.avast.com/index.php?topic=53253.0