While you do some new installations (of some software) in your PC, the intermediate files are extracted in a Temporary windows folder. Some of the software fail to delete these files. In some cases when the installation fails for some reasons, these files are not deleted by the program.
These files takes lots of precious disk space and also pose a threat to your privacy as any one can find out what activities are being undertaken on the PC.

A Window Washer or Window Cleaner Program such as CleanMantra eliminates these files and frees lots of invaluable disk space which have been taken up by Windows Temporary Files.