Using a not strapped HDD in a case that is slightly magnetic. [Be quiet 500DX]

Hi, I ran out of HDD slots and want to put in another disk in it. How bad / risky would it be to place my new drive on the bottom on my case. It is slightly magnetic, I don't know if it's from psu below or case itself, but you can feel slight magnetism, by dragging metal things through it like the drive or usb stick. Will disk shield itself enough for it to be irrelevant?