Thanks for the reply.
I had a look at the task manager like you said, it doesn't seem to be anything specific. I hope I'm doing it right, I have organised the processes by CPU usage.
When I click the start menu, or use the windows browser, I get cpu spikes, and explorer shows as cpu usage of 15. When I use firefox, it shows as 13. When I run an audio file in cubase, it sat at about 19 cpu. These numbers are in line with spikes, and they drop when I leave these programs idle. So, it seems to be just whatever program I am using, rather than one specific process.
None of the other processes seem to do much, although csrss.exe and 'System' popped up to 02 for an instant, but they don't seem to be in time with the spikes.