rijnton

Thanks again. It doesn't tell me what keys. But thinking about it I remember that some keys are reported every time again, no matter whether I delete them or not. So I think you are right.

Thanks krit86lr, My OS is Windows XP with SP2. I am the only user and always logged in as Administrator.

I use CCleaner already a few months and haven't had a problem with it until now. Today however I thought something went wrong after cleaning the registery with the Problems module. Although it turned out later that it had nothing to do with CCleaner, I first tried to do a restore, but that didn't go. When I right-clicked on the backup and on Merge, I got the following message (I translate it in English from Dutch, so it may not be exact): "Can not import. Not all data are written to the registry. Some keys are used by system or other processes". I also tried it in Safe Mode, but with the same result. Although I didn't need to do the backup, I still would like to know what is going wrong for later use. Thanks in advance.