How to make a bootable iso out of any files?

where do i get the boot files im trying to get it to boot like sardu or windows 7 disc . where do i get the file that makes it bootable can i copy boot.ini out of system32 folder will that make it bootable or where is the file located thats allows the computer to boot from something.us im trying to get it to boot without the c: drive starting. please walk me through the process. thankyou