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I recently bought a WD2500KS hard Drive ( Western Digital 250GB SATA-II 16MB Cache), and put Windows XP on it, i noticed the temps went up to 51-53C at one point, but much of the time in the high 40's... first impressions is that, a bit high isn't it, but im sure it's ok...? 
so i reassured my self and visited the Western Digital website and it states:
Temperature (Metric):
Operating: 5° C to 55° C
Non-operating: -40° C to 65° C
based on those figures, it seems a little high, considering it is in opertaing phase... however my other hard drive (exactly the same model) but without Windows XP installed, only used as a storage drive has temps of 40C... so it's because the OS is installed on that Drive which makes the temps higher?
so i reassured my self and visited the Western Digital website and it states:
Temperature (Metric):
Operating: 5° C to 55° C
Non-operating: -40° C to 65° C
based on those figures, it seems a little high, considering it is in opertaing phase... however my other hard drive (exactly the same model) but without Windows XP installed, only used as a storage drive has temps of 40C... so it's because the OS is installed on that Drive which makes the temps higher?