They must be really loud if you're having this much trouble. TBH I'd unplug each in turn to find out which is the noisy one, and then replace it asap. Modern drives aren't noisy unless there's problems - get shot and it'll save you a whole load of problems when it does go. My laptop HDD went yesterday, but thankfully our hardware support guys at work will do a swapout for me
It's very unlikely that both drives will fail at the same time, considering they are from different manufacturers. Without hearing the noise I couldn't really give you too much advice, but try running them without the case covers on and see if it's resonance through the case. Have you made any recent changes to the PC setup (hardware wise)>
Agreed. Because you will not expect to hear it, when you do it'll be very obvious. What Steve is suggesting is that minimising the use of the swap file (virtual memory on disk used when physical memory is at a premium) will reduce the times your HDD will need to be spun up. Sadly the latest Windows operating systems will use the swap file even if there is shed loads of physical memory available - I'd put it at 20-30% virtual in relation to physical. I can't say why exactly MS designed it this way, but I expect it was they predicted heavy memory usage of games and server style usage, so it was always designed to give equal physical memory usgae to all processes running, and because the OS's can't shuffle memory as well as MS would like, they split it into physical and virtual memory from the outset.