Hey COPC sorry to hear about your troubles. As you well know drives can be replaced and if its just a temperature issue then a change of fans could remedy the temp issue unless of course the sensors are the actual issue and not the fans or the temps..
You may want to install higher rated CFM fans and just let them run full speed. Of course the more air thats moved so to goes with the noise levels but if you have your server located in a remote location of the house where noise is not an issue then you could retro fit some big air movers that will keep the server cool. Typical 80mm fans move something like 15-35cfm but there are some that are rated for 84cfm and some have a speed controller which will allow you to balance air flow and noise levels but you would have to find a way to mount the POT.
Of course there is another more simpler approach to helping cool things down and its not exatly pretty but it does work and I use these fans in front of my Port Multipliers on Sun Night when all my hard drives are going to be defragged to help keep them cool. I have these small 4" fans that I place infront of the units with their doors open and blow air into the PM's. I have also done this with EX470's when the temps were going high and the existing case fans were not enough to keep the temp down even with Alexes Fan Speed Control. Now there is nothing wrong with Alexes program it works great but at this particular time my EX470 with a BE2300 was running hot due to a quirk in the HP Software that I could not resolve until I performed a server recovery and now its running fine. I picked up a bunch of these fans at of all places Walgreens and when they ran out of them I found similar fans at Target although the ones at Target were less expensive. So your looking at a $6-10 item that may just help keep your server running.
As for the hard drive it may just be better to replace it if its a problem. Personally I never use a retailers extended waranty this is often better done on the OEM side but over time as things go out of manufacture they will often try to replace or substitue the item with another as you have indicated.
The last thing I would mention is the COA Key on the bottom of the EX485 has value in that you can actually use it to install WHS-OEM on another unit and while the OS is not as cool looking as what you see on the MSS its still WHS and as by now you know can do most of what the HP MSS Software does with other software. So while it maybe a sad day for you, it can be turned around and become a much brighter day.
Just food for thought here and if for some reason your EX485 is beyond the point of salvaging then why not purchase a CFI-B43PM backplane and convert it to become an MSS PortMultiplier to run along side of your EX470 and if this is of interest to you then here is how you go about doing the conversion. http://www.mediasmartserver.net/2010/10 ... enclosure/