My system is Windows xp 2,2.5Ghz DualCore processor, 3GB Memory,Kaspersky antivirus. most of the time, my system is ok-no performance problem,but sometimes it hangs for a small time.It happens about 2 times in a hour.i can't catch the problem.

Have you tried control/alt/delete to bring up the task manager to see what is eating your resorces? Try booting into safe mode and run a complete virus scan and malware scan " If at first you don't succeed, Please Post Back "

A great malware scanner is Malwarebytes, @ http://www.malwarebytes.org/mbam.php " If at first you don't succeed, Please Post Back "

Well this is no Virus What are you doing while this problam occurs. Are you working on an application for a long time ?? You could check Taskmanager and select the cpu column so that the job that consumes the most CPU will always be on top.

First of all thanks for other answer. I am sure your system is corrupted by the window registry errors. Registry errors files is leaves from the uninstall programmers because of this your system is hanging. If you want to solve your problem then It will compulsory to you to Download registry easy. Then you can see how many errors in your computer.