Lower MySQL CPU Usage

I'm having a problem with high MySQL CPU usage on my server, one of my sites is getting hit pretty hard right now and MySQL is just killing the box. Its averaging a load of over 20, CPU usage is around 130%.

here is my my.cnf file. is there anything in their that should be changed to help lower the CPU usage?

# The MySQL server
[mysqld]
port= 3306
socket= /var/lib/mysql/mysql.sock
skip-locking
key_buffer = 256M
max_allowed_packet = 1M
table_cache = 512
max_connections=500
sort_buffer_size = 2M
read_buffer_size = 2M
read_rnd_buffer_size = 8M
myisam_sort_buffer_size = 64M
thread_cache_size = 8
query_cache_size = 32M
# Try number of CPU's*2 for thread_concurrency
thread_concurrency = 2

[mysqldump]
quick
max_allowed_packet = 16M

[mysql]
no-auto-rehash
# Remove the next comment character if you are not familiar with SQL
#safe-updates

[isamchk]
key_buffer = 256M
sort_buffer_size = 256M
read_buffer = 2M
write_buffer = 2M

[myisamchk]
key_buffer = 256M
sort_buffer_size = 256M
read_buffer = 2M
write_buffer = 2M

[mysqlhotcopy]
interactive-timeout
Server Specs.
Pentium E 2.0Ghz
2GB ram
2x 320GB hard drives.
Cent OS 5
Cpanel