alcohol will do great in cleaning. but then u have to make sure not to great static: e.g. using wool clothe. this is the reason why special liquids are used for cleaning the outsides. for the inside, normal paintbrush lang.having a dirty computer will not really destroy it will just have effects like higher heat inside the computer which most likely affect the cpu's performance. dirty fans, dirty heatsinks, more heat = slower performance. just my two cents.