I have a virus on my computer called Imminent Start Search. Every Monday, it replaces my default home and search engine and brings up an emoticon ad popup. AVG can't detect it and it's not in my control panel. I've looked up tutorials online but they all say to either just delete from your control panel, which I can't do, or download their own virus software. How can I remove it? It seems to be invisible on my computer and I can't manually delete it, nor can the full version of AVG.