Hello RichardHome!
It seems that you and Didactylos have entered a vicious circle. You don't know what to tell us about your machine to help, and Didactylos does not feel like enumerating all possible reasons for your machine being slower or excessively accessing the hard disk, if this is close to what you mean by "thrashing".

Fortunately Boinc is good also for easing your providing useful information.
Make sure you are using the advanced view and click on the Messages tab.
Once there, scroll back to the top of the list of messages.
Select all the startup messages from "Starting Boinc client..." down to the first "Starting (or restarting) task .....".
Then click on "Copy selected messages" in the leftmost column.
Last, use paste (Ctrl+V) in your next message to this thread and we will know everything we need to provide you with more useful answers.

Other advices posted while I am typing this post may be useful, but if excessive disk activity is due to memory swapping the "write to disk" interval will be of no help.

Cheers. Jean.

From the article, it seems that most drives use more power when actually doing something, but the amount varies tremendously - look at the Western Digital drives - almost no difference at all. That's pretty interesting since the only difference between idling and an io operation is the current to the voice coil and movement of the head - which has very little mass. But even with a 100% increase, you're still talking about at most 12-13 watts - ignoring the 10k and 15k drives - and even some of those aren't that bad (something that surprised me). If you keep the 60 second default for boinc hdd access - how much is that likely to add up to? It's not like boinc is continually accessing the drive for those 60 seconds. It's maybe a fraction of a second.

As for swapfile access, maybe if you're really low on memory and your system is bogged down doing memory swaps I could see it. Boinc can definitely chew up a lot of ram - on this machine it's over 100meg for 4 tasks. But even then you're talking about an additional 6 or 7 watts at most - which won't be the average for all users. Isn't that about what an old fashioned incandescent night light puts out?

I'm ignoring the 10k and 15k drives since these are performance drives and personally I wouldn't touch them. I'd use a solid state disk if I really needed that kind of performance. Plus I'm sure that the vast majority of people are still using 5k and 7.2k drives. But as I said, some of these aren't even that bad.

I have reduced my own HD thrashing on my X2 by installing a second hard drive. The first one still contains the OS and BOINC and the second now has the windows swap file/virtual memory and backups from other types of programs.

We are still not clear whether the original problem relates to thrashing (excessive disk head movement) or trashing (CPU dead). It might also be a fragmentation issue, which can also cause disk thrashing.

whining sounds like the fan at 100% CPU activity. That is by design, but the cabinet could be full of dust, causing noise.

Constant disk activity would have the disk activity light occulting instead of flashing.

$2 word definitions:
flashing - light is off more than it is on
occulting - light is on more than it is off