yeah...I got that situation and after ai post here' config. Render' and found out that the speed had increased enormously - I now realized it was just the first  renders..it's back to the normal slooooooooow render behavior.
Got the Task MANAGER open and I can see it's using 4% the QuadCore. Ok sometimes uses more than 90% CPU and almost 3GB ram but still not so quick ...
I wonder if it's something to do with the external drive become hot after some hours of use or.....?
Could that be?
Anyone has anything,any clue if could be that? Not the PC itself but the external drive.
Please if you know for sure that is what it's - post here. If you're not sure don't. I already made some costly mistakes because I did follow the lead of one or three here - we got to be careful what we said about things we're not soooo sure about..some people may follow our advise and go broken! 
Otherwise, I do appreciated the experience of one that has same problem as I.
Thanks sincerely.
Cris

"'you shut up!  or I'll bring democracy to your country! "
Cris Galvão aka Softcris  - www.crisgalvao.com
(or softcris, SoftCris)
Rendering since 1997 and
at Renderosity since 1999.
OS Win 8.1     64 bit

I run Poser from an external. I haven't noticed heat issues, but I do know it works better if I open the case and get all the dust and gunk out every few weeks, I have lots of critters. Certainly all that dust isn't from ME! LOL.

-Sarah