W2K Srv – CPU Utilization is constantly

I have a dual pIII-800 w2k srv box acting as one of my file servers and the cpu utilization is constantly >50%. I have checked to make sure that it sees both cpu’s and it does. I turned off my anti virus and it doesn’t even go down lower then 50%. What other steps might I try to check out, or what other counters might I check in perfmon? I have another single processor file & printer server also acting as a app server and it’s the PDC.. and the cpu rates are normal for it. >10 percent mostof the time with antivirus running.
Thanks in advance.
Jim S.