Sometimes when normally using my PC, it will (seemingly) randomly slow down, and maybe sometimes even freeze for several seconds. During this slow down period, it looks like a (I don't know which drive it is) hard drive is constantly being written to. During the last slow down, I started Windows's Ressource Monitor and found out that the System process was writing up to 10MB/s to a drive (I suspect it's the system drive, C:\, but I don't know for sure).

I'm not doing anything unusual (at least, I don't think I am), and most of the time, it will work normally, but, as I said, it just randomly slows down for some times. Any ideas on what might be causing this and how I can prevent this from happening again?

(I have a triple-core processor and 4GB of RAM. My system drive is a WD Caviar Black 500GB, my secondary, 'data' drive is a Samsung drive, which I don't know the model number of, but I can look it up. I can also post my full PC specs if needed.)