Hi, I was wornding if any one could point me in the right direction for programing system files. The reason I am interested in this is because I was just wornding when they are called how/what runs them. I know the systme runs them but if i make a batch file and name it .sys if i try to run it I would get a message asking me what I want to use to run the file why is that, why dosen't the system try to run it an crash.