Heavyload is inteded to stress all resources of a PC (like CPU, RAM, harddisk, network, operating system, etc. ) in order to test, if it will run reliable under heavy load.
This is useful for testing important NT file or database servers before using them productively, or just to check if your new PC might get too hot when used intensively.
To stress your PC or server, HeavyLoad writes a large test-file to the temp folder, it allocates physical and virtual memory and it draws patterns in its window.