DLL Cleaner
The usage of dll as a library of codes and data for any program that needs it saves disk space and allows efficient memory usage. Still, it can create a disk space issue when a dll file is no longer used by any program. The number of these unused dll files can grow over time. Unfortunately, there is no easy way provided by Windows to find the obsolete dll files. If you delete a dll file that is still needed by a program, the program may not be able to perform its functions due to the dependency.
DLL Archive is a free dll cleaner. It scans, checks and verifies all existing dll files to find the unused ones. Still, it doesn’t mean that all dll files that are added into the list are 100% unused. There could be a chance that any of the dlls are still needed. That’s why DLL Archive archives the dll files. This backup allows you to restore any of the dlls.

If these most likely unused dll files are still kept within my hard drive, how could I save my disk space then?
The option you have is to keep the dll files for a certain period of time within the backup directory of DLL Archive or move them to other storage devices like a flash drive. See if you find any error within this period. If nothing goes wrong, then you can delete these dll files.
DLL Archive is a dll cleaner that works on all versions of Windows, from Window 95 to Windows 7, including Windows XP, Vista, Win2K, etc.