WinDriveSpace

WinDriveSpace helps Windows users gain additional disk space without deleting files. It compresses suitable existing files using the file-compression functions built into Windows, so users can continue opening and working with their files as usual.

Its intelligent process skips very small files, files that are already compressed, and file types where compression may be undesirable, such as SQL databases or virtual-machine disk images. The operation can be stopped, and the app also provides a decompression function. Some core features require administrator rights.