What model of hard drive do you have?

Hitachi HTS545050A7E380

Open up the Reliability Monitor (it's a program that comes with Windows).
... ...

If it's an app, try uninstalling the app. If it's a driver, try rolling back the driver. If you don't see anything suspicious, perform an exhaustive RAM check. Then check the SMART status of your hard drive.
You may be able to find more details for BSODs in the Event Viewer, but there's a lot of stuff in there and your BSOD may be hard to find.

RM Very useful tool

I think you can cover the security issue by using a archiving (7Zip, WinRar, Etc) (even if it is just using the minimum compression ratio) to and encrypting the contents.

thanks for this suggestion

You mentioned that the crashes are more frequent now. Is there an average (even a rough guess at one) up time your machine has between crashes? If it's reliably a couple of hours you can index the files on your hard drive (a powershell script would do it just fine, and quickly) and then set up a schedule to compress/upload/copy-to-thumb-drive pre-sized chunks of data in order of importance. It would suck to be in the middle of backing something up and then have your computer do a hard restart and corrupting your backup.

The frequency of the crash varies wildly - I think my usage signature plus specific data - run program, usb usage, browse... - play a strong part in triggering a bad sector. Your suggestion is a good one wh, ... i would find a way for.

Using "WhoCrashed" tool to read dump files as frob and Code Fox suggested is I am setting about doing now

WhoCrashed is the easiest tool for reading dump files - and it's free !

Does any one know if microsoft's onedrive is a good place for backups, particularly considering security and privacy issues?

I heard onedrive defaults to your c drive meaning not a good place to backup to if your c drive is the culprit

If BAD_POOL_HEADER is too generic,

You may try disabling hardware to minimum set to see if problem persists, also you may consider something like Hiren's CD to check memory (memtest) or HDD (either utilities or using Windows XP/7 "Live" version)

Hi. Is something over heating in your computer.

Section of Hard disk is bad, Any help on how I could fix/repair disk -Hitachi HTS545050A7E380, (can't afford new one at the moment). BSOD is now so relentless, coding any work has been practically impossible for me.Thanks for any help

If a harddisk is failing you should copy all important data to a different drive as soon as possible. Harddisk failures in progress don't get better, they get progressively worse until you are unable to access any remaining data.

If you are unable to get a replacement drive or comparable data storage unit right now do not use the system. Nothing is good for a dying drive but I'd rather have it lying inert than used if there is no other choice.

If replacement isn't an option atm,

Once bad sector started it always gets worse but a temporary solution would be not using "that" part of disk by creating an unused separate partition. And no need to remind to backup vital data

If a harddisk is failing you should copy all important data to a different drive as soon as possible. Harddisk failures in progress don't get better, they get progressively worse until you are unable to access any remaining data.

If you are unable to get a replacement drive or comparable data storage unit right now do not use the system. Nothing is good for a dying drive but I'd rather have it lying inert than used if there is no other choice.

Damn!!! So I have got no choice but to pack it up, for now... or at least till I can afford a replacement, ... and this computer is only ~ 2.5 years old. Hmm, anyway thanks

If replacement isn't an option atm,

Once bad sector started it always gets worse but a temporary solution would be not using "that" part of disk by creating an unused separate partition. And no need to remind to backup vital data

Since its only going to get worse, maybe I will just have to pack it up until I can afford a replacement, thanks

If the drive is useless anyway, you can also attempt a low level format. If the drive failure comes from a damaged magnetic surface it won't help, but it is comes from a misalignment of the heads it can restore your drive. Of course it will also wipe all data and if done from Windows you need another working drive to boot Windows on.
I can't find a low level format utility on the Hitachi web site any more. There is WinDFT that has an "Erase disk" option but it's unclear whether it's really low level format. There are also other utilities on the net to do that (some of them shareware).
In any case this is a last resort solution. It may give your drive a few extra months, but even if it works the drive should still be considered extremely unreliable, so backup often ;) . Still it may be an alternative to just packing it up if you need a working computer.