Laptop takes longtime to turn off

I am using a LG laptop running on Windows XP. I had some issues virus issues in the beginning, and hence I had re-installed OS 3-4 times. But recently,I have an issue – i.e,whenever I click shutdown/restart, it takes sometime to either show the shutdown / restart window. And sometimes it comes up
immediately. I guess,the window comes up immediately, if I don’t use the system for a longtime. Can anybody please suggest some ideas to fix this issue ( I am tired of re-installing the OS again and again)