On a Windows PC, the hard drive is low on disk space. Upon investigation we find that each user folder that is created increases the disk usage far more than it should.

Log in as Administrator.  Check for un-needed files or folders under the Users\Default folder.  The contents of this folder are duplicated within each new user folder that gets created as new users log onto the computer.  So, for example, if 5 GB of files are in the \User\Default\Downloads folder, then those 5 GB of files will be duplicated into each new \User\ folder.  

To delete the files from the \Users\Default folder, and then from all other user folders that have been created, browse to the offending files and delete by clicking Shift-Delete.  

For any case where hard drive space is an issue on a Windows PC, it is also a good idea to run the Disk Cleanup utility.