Does pf=Page File? If so, you may not have enough RAM, and your system is spending a lot of time swapping to and from its hard drive.
If you think that doesn't make sense because you have a lot of RAM (say, at least 4GB), it is possible that your memory has become fragmented over time. A shutdown / restart should fix that little problem. I would recommend doing this at least once per week, even if you leave your PC on 24/7.