I have windows 2003 server with SQL Server installed on it for live calls billing but the CPU utilization is reaching the maximam and it's average above 60% which is causing lot of problems specially for the live environment. I have enough memory and free hard disk space is more than 40GB,
How much CPU is SQL Server taking (according to Task Manager)? Anything else installed on this box (IIS)?
If SQL Server is taking up the majority of the CPU, then run a few traces in profiler, to see what is doing all the work. Look for queries that run with more than say 100 reads. That may give you a place to start from.
We can't diagnose this problem any more than a mechanic could figure out what is wrong with your car just by you telling him that "it doesn't run well".
You have three options here:
1) Throw hardware at the problem by getting faster processors.
2) Read SQL Server Books Online and learn how to use SQL profiler to identify inefficient queries, and then learn advanced SQL programming techniques to optimize those queries.
3) Hire a dba to help you with this.
If it's not practically useful, then it's practically useless.