you can easily install bt4 on your hard drive without dvd-rom drive, but with something like a ...usb key
First I have to say that you have a menu just behind the header of this page, with some links, one is "How To", I suggest you to try.
You can also find other informations about this question on google easily.
You will need a usb key, a valid iso of the BT4 final, and some time, but it is really simple I give you an extra keyword to play with "UNetbootin", might be usefull to your query.
As we say here "try harder", and you will get the pot.