My computer came with only one hard disk drive: C. It has a capacity of 920 GB. And I have used 80 GB of it. 

Now I want two drives in my computer: C and D. But I want 150 GB in the C drive and the rest (770 GB) in the D drive. And I don't want that any files that I currently have in my C drive get deleted. How can I do that?

(I can't back up at the moment, because I already installed a lot of software and customized the operating sytstem. That's a lot of work.) 

Thank you.