This Halacha is an excerpt from our Sefer
Buy me here or on Amazon.com
Must one undo the keyboard of his computer to remove the Chametz stuck under the keys?
No. This applies even if one knows for certain that there is Chametz found there. Nevertheless, in light of Yisrael Kedoshim Heim, those who desire to be stringent and undo the keyboard are not to be protested. In any case that a thorough cleaning was not done, it is strongly advised not to use the same keyboard on Pesach as that used during the year, as it is possible for Chametz to get onto one’s finger and end up in one’s food or mouth.
 As a) The Chametz is unreachable by hand, and thus nullification alone suffices. b) The Chametz found there is less than a Kezayis and is certainly dirty. Due to the second reason, it is not required to even shake out the Chametz, if possible.
 See Michaber 442:6