HDF and WHDload are totally different things.
HDF is an image (like an iso) of an installed program and can be used AFAIK only with winuae. HDF are common for Mac system.
WHDload is a program to permitting games not-made-to-be-installed to be installed. You need the WHDload package to run them (and consider registering as it is a great program). Usually the slaves required some fast ram to run.
Lio
