Formatting old system drive

[foreright]

Bear with me guys if I ask a couple of dumb questions.
After building new machine with only SSD in situ for the OS. I intend putting in 2 HDD's from old PC.
One had music and data and poses me no problems. But the other one had my OS and programs on it. Firstly on installing it. Will boot up ignore old OS on it. Secondly how can I format it to rid anything they may remain in the bowels of the HD.
Can you also tell me if by default all programs and documents will install and save in the SSD and if so what will store on the newly formatted HDD.
Hope you understand what I'm waffling on about and can help me - Cheers.

 

[foreright]

Does a basic format purge the old HD of all data or do I need a third party utility to deep clean (so to speak)
Is there any disadvantage to installing programs to HDD so as to keep the SSD exclusively for OS etc.

 

[foreright]

Thanks for your time wazza. One last question is "basic" what I would know as "quick" and how do you acheive a "full" format. Is the utility with Windows sufficient?
Sorry another one. You say make a folder to install programs on HDD, would that have to be called "Program Files"