There are my results (CPU stress 100%). I bought 40x40 mm fan (6500 rpm , 31 dBa) and placed in blue rectangle from this post:
My single drive silent NAS HP T5740 thin client build
Results is too small for use fan - my fan was very noise !
I dropped my idea and remove HDD from Thin Client. I use Debian instead windows - debian need less space and I installed on 4GB disk.
I bought 30x30 mm fan and USB cable to create this.
After test I will write results 
I tested my Thin Client (t5570e) on CPU stres -> CPU about 70*C and HDD about 50*C (it was short test, about 20 min).
The reason for high temperature for HDD is the HDD has been screwed to top, metal plate (radiator for CPU). HDD is very close to radiator of CPU (red rectangle).
Maybe should I glue additional radiator to the top, metal plate instead add fan - bue rectangle (i'm thinking about 40x40 mm fan, only for air flow inside - connect by internal usb) ?
In normal work, I think taht HDD has close 50*C and CPU 65*C.
Hi
What about temeprature?
I have installed HDD to my Thin Client and sometimes I have high temperature (CPU - 65*C ; HDD- 49 *C).
Maybe I should byu small fan or radiator to glue on metal top element of case.
