Unfortantly as one man can build it another man can take it apart (or woman for that matter).  The best way to keep a computer truly secure is to lock it in a vault and take a fire-ax to the internet connection.  But even then there exist devices that can sense the feedback from monitors and computers over electrical lines and rebuild the data.  The ultimate security for infomation would be to let only one man compile and work on the project, have him eat all the data and then shoot him in the head and burn the body.  Bear in mind the time table of project using this security method can become quite lengthy and the legal implications will not be discussed here.