Why do I have excessive advertisements in Chrome and Firefox?

[chickenlad7db]

Now, don't get me wrong, I know how many ads are usually on a page. I still have the regular ads but in addition to those, I have 3-4 more ads. I have a banner pop up across the top of my screen and at the bottom. And then Banners that pop up on the side, basically creating a border of ads around my screen. Then a lot of words ( text on the website I am looking at) are highlighted blue and whenever my cursor hovers over the word an ad pops up next to my cursor. I also sometimes when I use a website, like a search engine, that whenever I hit enter to start my search I get redirected to a new webpage that is a lone advertisement. There are so many ads that my web processors are slowing down and becoming nearly unmanageable. I haven't wanted to uninstall and reinstall the browser in an attempt to save my massive amounts of bookmarks, but I don't know what to do. I have used my anti-virus program ( Kaspersky) to scan my entire system but I have not found any sort of virus on my system. I have never had a problem with before but suddenly it started happening. In chrome, I have also randomly stated downloading something called "Update.exe" even though I did not accept any download. It randomly downloads an executable without my permission. Ever since that has happened, I have been scared to even use the internet on that computer in fear of what is happening.

The ads are on Google Chrome and FireFox.

Any suggestions?

Thanks.
EDIT: I have checked my extensions and there are not any installed other than Kaspersky.. I even have it set to maximum internet security and ads should be disabled...