Reasonable NoClone 2010 is a program that will find and delete duplicate files. This way you will recover the space they occupy, which you can now use to store more information.
You can configure the program to look for duplicate files in entire drives or just in a folder or group of folders. The search can be limited to a certain type of files (say, .MP3, .DOC, .XLS) or open to any file. You can choose to search only for files bigger than 1 MB, of for any files regardless of the size. It is even possible to determine which paths will be excluded from the search.

Reasonable NoClone can also scan your Outlook messages base looking for duplicate e-mails.

The "Smart Marker" feature will let you mark files according to a given criteria (date, size, or length of the file name). Once the files have been marked, you can use the “Save Space” feature to recover the space taken by them.

This review applies to the Home Edition. You can refer to the developer’s page to acquire the Enterprise Edition, with added features. Actually, the only differences are that the latter supports Windows 2000 and 2003 Server, and that it does not limit the network paths to 3 and the files in a search to 300000. The unregistered version of NoClone will just delete thirty files per action.