CPU usage 99% - and query very slow - help

[irox ferenc]

Hello i have Tables with 2G of data in (1,932,758 records),
all tables have indexes and are optimizaed every 3 days.

I have this dedicated server:
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CPU Intel(R) Core(TM) i5-2400 - 3101.000 MHz
Cache : 6144 KB
RAM 4 x 4096
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MYSQL: Versione del server: 5.0.95-community-log
PHP: 5.2.9

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and this is my.cnf
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[client]
#port = 3306
#socket = /var/run/mysqld/mysqld.sock

[mysqld_safe]

#socket = /var/run/mysqld/mysqld.sock
#nice = 0

[mysqld]
log-queries-not-using-indexes

bind-address = 127.0.0.1
#lower_case_table_names=1
low_priority_updates=1
tmpdir = /tmp/
key_buffer =800M
max_allowed_packet = 2M
table_cache = 3212
max_connections=150


interactive_timeout=60
wait_timeout=60

innodb_buffer_pool_size = 0


hot.key_buffer_size = 250M
cold.key_buffer_size = 64M

join_buffer_size=32M

sort_buffer_size = 8M
read_buffer_size = 5M
read_rnd_buffer_size = 5M
myisam_sort_buffer_size = 64M
thread_cache_size = 8M
#query_cache_size = 64M
# Try number of CPU's*2 for thread_concurrency
thread_concurrency =8


query-cache-type = 1
#query_cache_min_res_unit=200K

query_cache_size = 65M

query_cache_limit =250M
tmp_table_size=256M
max_heap_table_size =250M

log-queries-not-using-indexes =/var/log/mysql_slow_no-indes.log
long_query_time = 1
log-slow-queries = /var/log/mysql_slow_query.log
[mysqldump]
quick
max_allowed_packet = 16M
low_priority_updates=1

[mysql]
no-auto-rehash
#safe-updates

[isamchk]
key_buffer = 125M
sort_buffer_size = 256M
read_buffer = 2M
write_buffer = 2M

[myisamchk]
key_buffer = 125M
sort_buffer_size = 256M
read_buffer = 2M
write_buffer = 2M

[mysqlhotcopy]
interactive-timeout