lots of unnecissary files and programs

I have an HP Pavillion dv5. I have had it for about 5 years or so and have A LOT of unwanted files and programs on it. I would love to do a factory reset on it but it only lets me restore from a preset backup date....which the earliest one is in 2012. If anyone knows how to sucessfully preform a factory reset let me know. If not I at least need to find out where to go and how to delete my unwanted files and programs. Thanks in advance.
P.S. I am not a techy so act like you talking to a four year old please. Haha