Dying HDD or ?

[Mise]

Hello,i have two HDD one is Hitachi and the other is Seagate.Both are 500GB Sata III.

The main problem is i get wierd sounds like opening a folder randlomly when i play games or just searching something on mozila or chroome.Someguy told me that my hdd is dying but i thought that this is some bug from the Win 7.

-Today (After 1-2weeks) i have noticed that the the space on my Hitachi HDD is getting too low i mean one day is 88GB and after some time is 87.6GB and its getting lower and lower every hour ? (I am not downloading anything...)

-Every HDD is vibrating and that its okay but today one of my HDD just vibrated so loud for 3-4 seconds...i though that the hdd will get out from my case.That happend 3-4 times,just so strong vibration.
-Opened HDTune pro (also Speccy) and there is no problem with the 2 HDDs   + Last month i have scaned the both of the HDD and there were not bad sectors or erors just the Seagate was quite faster than the Hitachi.

Just please dont tell me that the HDD is dying  
Should i format the HDD or remove it from the pc and put it on another slot or change the sata port on the mb ....   ?