Yes, it is supposed to do that.
give ccleaner a shot its better and has more features for cleaning...
DLL's can be deleted safely only if they are no longer needed by the programs referring to them.
Yes, there is no harm in deleting these files. I delete mine all the time. When you perform a system maintenance, these files are deleted at that time as well.
Cleanup does delete some files... Even more if defragmentation process was incorrectly interrupted or computer unexpectedly rebooted you will loose some data in some cases without chances to get it back.
DESFRACMENTAR
The .tmp extension is a TEMPORARY file.Often these files are created during the installation process or during cleanup procedures.Sometimes by changing the extension you can open them in some program or other.If they are old they can safely be removed.
It is just important to recover deleted files that are needed.
Join.me can see your screen but can it see deleted files?
Disk Cleanup
removes unnecessary files
removes unnecessary files
You can check your recycle bin if deleted files are still there but if your files are permanently deleted then you should go for a recovery service. I have tried Stellar data recovery service to get my important files. You can go for it too.