excessive SMB traffic

I’ve been experiencing, at seemingly random times, massive slowdowns on my Server 2003 machine (to the point that all I can do is reboot the server). I’ve finally figured out that during those slowdowns, there’s an excessive amount of SMB traffic between the server and my desktop pc. When it’s running normally, I don’t see that SMB traffic. I’m still trying to figure out all the info that wireshark gives me, but does anyone know what might cause the sudden increase in SMB traffic?