You may want to delete old data to save up space. Temporary files for example. If you have such files, there is an easy way to do this only with Microsoft tools. You may have to install the Windows Resource Kit for your version of Windows first.

With the forfiles command, you can list files matching some criteria and execute a command for each file found.

For example:

forfiles -p "C:\<path>" -s -m *.* /D -<days> /C "cmd /c del @path"

will delete all files in <path> who are older than <days> (mind the - before the amount of days).