For some reason Windows 8's Task Manager reports spikes of 99% disk activity for hours at a time. Looking at the entries in that column, however, data doesn't seem to be getting written any more quickly than when the disk activity is around 25-50% (which it seem to idle at most of the time).

Furthermore, when these 99% disk activity spikes are happening, the average response time reported in the Performance tab becomes 4000-6000ms.

Is there a good way to find out what is causing the disk activity? I've tried using Process Explorer, but I said above, the rate at which data is reportedly being written doesn't seem to correspond (Dropbox and Google Chrome are constantly the top two, but the spikes are not dependent on their being open).

Thanks in advance for any help. It gets very annoying when the computer stutters to a halt.