Hi listen to this song about erasing unhappy memories http://www.youtube.com/watch?v=4U0ezpvm4LI

Imagine a computer with 0 memory. Not even with a hard drive! Piece of useless crap. Now, human brain is even more complicated. If you want to erase the memory in order to get rid of sadness, then you have a problem right here. As the ancients said "If there wasn't black, how would you know what's white." Same goes with sad/happy contrast. Every single memory is making you who you are and losing one I'd consider a tragedy.

Hello Jiabao, Denis' answer is very remarkable. A drug is being developed nevertheless to eradicate and selectively delete certain memories or at least block them.Particular memories has been erased in experimental mice already. So it may be soon possible with humans.It will target removing only specific set of neurons that store a particular memory. The question remains what is a human being with a missing part of his memory ?! Memory is essential to a person's identity and erasing bad memories takes away an important part of him and how he chooses to act!!

Interesting, but the idea that a particular memory is stored in one specific place in the brain is a misconception. Memory is a process that extends over the entire brain. Let's say that you recall being bitten by a dog when you were young. The memory of the color of the dog is stored in one region of the brain, the memory of the pain in another, the memory of the dog's bark in yet another spot, and so forth. The remembering process is actually a complex brain-wide reconstruction of the event, which is similar to a hologram. If you erase one piece of the dog bite memory, it can reform again using information located elsewhere. Our memories are an integral part of who we are. Without them who would you or I be?

thats my favorite movie actually..