I intend getting rid of my old desk top computer, scanner and printer. They all work perfectly well, but I only use my lap top now and as I have a new scanner/printer, the others are now superfluous.

They're all too old to sell so I intend giving them to charity.

My questions are :

How do I delete all my files, emails etc, from the hard drive so the new owner cannot access my computer history?

Do I need to delete every single file one by one, or is there a quicker way? I have never cleaned my hard drive because I don't know how but I do clear my browsing history on shut down, but that's about the extent of my cleansing knowledge.

I have noticed an option to restore computer to factory settings. Is this what I use? Is there another way to delete everything?

Also....

I added more RAM to the desk top computer a little while back, by way of another card. Should I leave it in, or should I take it out before getting rid of the computer? If I remove it... how do I keep it, seeing I no longer have the magnetic (or anti-magnetic) pouch it came in?

I can't remember how many extra oomphs I added, but it was probably 2. The only reason I'd take it out would be if some-one else (or me) could use it. Might that card fit my laptop, or are the notches on the sides particular to desktops ?

My desktop is an HP pavillion, and my laptop a Dell.