Acronis Drive Monitor - Critical Events

[#1]

Just wondering how reliable the warnings from Acronis Drive Monitor are.
It is currently reporting a problem with one of my 1TB drives.

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Critical events: High risk events detected

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Warning Disc internal temperature has increased above the safe range. Old value: 42C, New value: 43C

Also see jpgs below:
This is an internal drive in an external casing (no fan). 43C does seem very high. Other drives are showing around 26C.
I have noticed that drive access has slowed down over the last month or two. I have ordered a replacement to copy everything to just in case.
Also, without opening the case at present (the less it's moved till I get the data off the better I am thinking) is there an easy way to obtain the serial number so that I set up an RMA to Western Digital> (I now maje a note of all serial numbers before putting them in cases 

[#2]

Download and run speccy for the Hard drive serial number.http://www.piriform.com/speccy

[#3]

Thanks Steve.
Unfortunately, Speccy only seems to find the internal drives. Can't seem to find any option for the external ones
Edit: Found them under Peripherals - no serial numbers, though.
Edit 2: Forgot I have Sandra Lite installed but that doesn't list the serial numbers of external drivers either. Got the info from Belarc Adviser