Getting your child to part with toys?

My daughter is almost 5 and I can not get her to give up toys. Her room has become overrun with toys, toy pieces, and stuffed animals.. There is literally no room. Many of the pieces are small parts and missing pieces to things that are broken or missing. Half of the things she no longer plays with because there is so much stuff she forgets she has them! But when I try to do spring cleaning to take some of the old toys to the goodwill, she freaks out, cries and doesn't want them to go. I don't want to just take them away and have the problem/fear become worse.. How can I get her to part with all this old stuff??