Msconfig is inbuilt utility in win 98SE , win XP , win ME , This very good utility to stop the programs on start up , b'cause when ever you boot ( start ) your computer loads, all the hidden softwares and programs .
Usually there are lot of programs that start automatically every time you boot your computer , even though you don't use those programs much ,
these programs takes system resources and RAM ( memory) . your may slow down , so it's always better to stop those programs or services , which are not in use .
when you change any start up programs , or start up services , the changes takes place only after you restart your computer .