I'm also a hoarder. Well with dvds that is yes it has to do with Ocd which I have so your friend might need help.
Hoarding is not a "problem" per se, it is a symptom of a psychological issue. Until you deal with the emotional/psychological problems causing the symptom, you will not be able to help the hoarding.
Professional help and sometimes they don't want help.
I know three and there're very happy being hoarders.
There are some online support groups for both the hoarder and their family, there may be local meetings in your area. There are also some good videos online that explain the psychology of hoarding, this may help you understand why a hoarder struggles to get rid of things, they tend to develop an emotional attachment and also struggle to prioritise, they tend to place importance on everything they hoard. I have a friend who has it.