mysql if using too much CPU of my VPS.

Can anybody help me?
Basically my app is for an email marketing, so using a while statement its reads from a db (mysam) and make updates

Thank in advance!!

This is the info about my VPS (when typing )
Intel(R) Core(TM)2 Quad CPU Q6600 @ 2.40GHz
Intel(R) Core(TM)2 Quad CPU Q6600 @ 2.40GHz
Intel(R) Core(TM)2 Quad CPU Q6600 @ 2.40GHz
Intel(R) Core(TM)2 Quad CPU Q6600 @ 2.40GHz
Mem: 1206272 kB
OS: CentOS release 5.3 (Final)
Mysql: 5.0.45-log

This is my my.cnf:
[client]
port = 3306
socket = /var/lib/mysql/mysql.sock

###The MySQL server
[mysqld]
set-variable=local-infile=0
port = 3306
socket = /var/lib/mysql/mysql.sock
ft_min_word_len = 3
key_buffer = 32M
max_connections = 400

log-slow-queries = 1
log-queries-not-using-indexes = 1

key_buffer_size = 256M
query_cache_limit = 10M

long_query_time = 5

join_buffer_size = 3M

max_allowed_packet = 32M

table_cache = 443

sort_buffer_size = 32M

read_buffer_size = 10M

myisam_sort_buffer_size = 32M

thread_cache = 4M

wait_timeout=500

connect_timeout = 300

interactive-timeout = 1200

query_cache_size=256M

query_cache_type = 1

thread_concurrency = 8

max_user_connections = 300

log-error = /var/log/mysqld.log
old-passwords = 1

skip-bdb

set-variable = innodb_buffer_pool_size=2M
set-variable = innodb_additional_mem_pool_size=500K
set-variable = innodb_log_buffer_size=500K
set-variable = innodb_thread_concurrency=2
[mysqldump]
quick
max_allowed_packet = 2M

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

[isamchk]
key_buffer=200M

sort_buffer_size = 4M
read_buffer = 2M
write_buffer = 4M

[myisamchk]
key_buffer = 4M
sort_buffer_size = 4M
read_buffer = 2M
write_buffer = 4M

[mysqlhotcopy]
interactive-timeout