I've installed the latest Version 3.04.1389 over my last version 3.03 and this newest version is either corrupt or has major flaws. I'm running Win XP and when I go to find registry problems it keeps generating false invalid or empty file class registry values. They registry values are very strange in nature with weird file extensions that don't relate to any software on my computer and they all have "open with progids". The first thing that entered my mind is that I have somehow been invaded with a computer virus and started emergency action. However, nothing came up in my virus programs indicating any virus or spyware problems. I decided to install this new version CCleaner on another computer running win xp and the same problems came up on that computer as well. To my relief I now new it wasn't a computer virus or something worse. Reinstalled the older version of CCleaner 3.03 back on both computers and the program is running back to normal as it has always done.
It's a known issue many people are reporting, just untick in the registry cleaner: Unused File Extensions
I also have CCleaner with WINXP SP3 and all updates. I downloaded the latest version to my Desktop (I send that to a Flash Drive), remove the older version and install the latest version 3.04.1389 and it went smooth. I don't like to put a newer version over an older version. Some of my items will remove the older version or update to a newer version but I do not see a necessity for anything from piriform, I don't touch Comodo Internet Security but lavasoft also has antivirus engine that I uncheck but the following updates to a newer version: 1] Adobe Reader 2] Malwarebytes' AntiMalware and 3] SuperAntiSpyware.