counter strike 1.6 falls fps

health

I have a problem with a particular fps when playing from the beginning I have 99 fps, then drops me to 40 to 60 (less lag) and again at 99 and so still ....

I try?
steam I tried to install anything
raty set
drivers update
computer purified
registers as well
off all unnecessary + game booster
no viruses + spyware
RIST log clean
hight fps models + fps config

Reinstal windows - rejected

PC:
processor
Intel Pentium Dual Core P6200 with 2.13 GHz frequency
2 x 256 KB L2 Cache
3 MB L3 Cache
2 cores, 2 threads
Max TDP: 35 W

Memory:
1 x 4 GB DDR3 1066 MHz
Up to 8 GB in two slots

Graphics:
NVIDIA GeForce GT520M with 1024 MB of onboard memory

Display:
15.6 "TFT LCD with LED backlight Glossy
Resolution: 1366 x 768 points

Hard Drive:
500 gigabytes
5400 RPM

Optical drive:
DVD SuperMulti

Multimedia:
Built-in speaker
1.3 megapixel webcam

internet:

http://www.speedtest.net/result/2140915113.png

translated by Google Translate
because I am from Slovak

Do you have an antivirus? if so, disable it when playing and see if that helps.