Do what sheath said mostly. Clear un-needed things from your browser.
As for a different brand, Comodo Antivirus is a good choice, it's what I use, sometimes it can be a bit overprotective. (Which I like about it) '
Like when I try to open a file from an unknown publisher it pops up with the options. "Allow, Block, Sandbox" (Sandbox allows the item to be run without it damaging your computer, and if there is a virus, you can Disinfect it (Some viruses don't have this option) or quarantine it (The file cannot be opened at all, you can not download it, infact I think the site download turns into a 404 error page.))
But this isn't about Comodo, I wish you well with the problem.