svchost.exe is using too much cpu, almost 50%, i checked it with Process Explorer (from Microsoft Sysinternal Suite) and i found that it's NlaSvc Service is causing that, i can't stop this service because it's an essential windows service.
I uninstalled somes softwares wich i suspected to cause this : antivirus, nokia ovi suite, riva tuner, adsl autoconnect, nothing changed.
I upgraded my drivers
: lan, sound, graphics, nothing changed.
i'm sure that i have absolutely no virus.