dis•ap•point•ed /dspntd/ adj. ~ (at / by sth)| ~ (in / with sb/sth)| ~ (to see, hear, etc.)| ~ (that ... )| ~ (not) to be ... upset because sth you hoped for has not happened or been as good, successful, etc. as you expected: They were bitterly disappointed at the result of the game. I was disappointed by the quality of the wine. I’m disappointed in you—I really thought I could trust you! I was very disappointed with myself. He was disappointed to see she wasn’t at the party. I’m disappointed (that) it was sold out. She was disappointed not to be chosen.
As you can see, there are many options to choose from. It´s a matter of context which preposition you have to choose.... I hope that these examples help in choosing the correct preposition. I am not a native speaker, but maybe someone else has good advice to give for the notion "disappointed".
with myself, in another.
Hello.
Kiefer Sutherland said, "... disappointed in myself..."
http://www.cnn.com/2007/SHOWBIZ/TV/10/10/sutherland.arrested.ap/index.html"I'm very disappointed in myself for the poor judgment I exhibited recently, and I'm deeply sorry for the disappointment and distress this has caused my family, friends and co-workers on '24' and at 20th Century Fox," Sutherland said in a statement.