well now I'm getting the same error when I try to install older versions as well. It's a shame that they can't get the bugs worked out before releasing a new version considering this one clearly messed up my entire process. @hazelnut, I tried to follow the article in that forum post but there is no ccleaner file in my program files anymore. When the last instance uninstalled, it deleted EVERYTHING ccleaner related. I guess I'll just have to clean everything manually daily or stop using my main computer until a new update comes out that fixes this problem