I will be showing you how to access and use MSCONFIG on Vista in this post, the procedure for XP is almost the same.
How to use MSCONFIG
1 ) Press the start button and type msconfig in the run box (for XP click on Run and type it there)
2 ) If the UAC popup appears, press continue.
3 ) This will bring up the MSCONFIG window. Click on the Start Tab.
4 ) You should see a list of programs that are set to run on startup.
5 ) Uncheck the boxes for programs which you do not want to run.
6 ) If you are unsure about a program its best to check the command column and see where the program is located. This will give you a good idea on which program it is.
7 ) If still unsure check this list http://www.sysinfo.org/startuplist.php. It contains a list of 17654 startup items.
8 ) Once you are done, click the Ok button and choose Restart.
Personally I removed unwanted startup items like, Adobe Reader, IM messengers, etc. By having only needed items running on your computer, it will make it much faster. Even if items aren’t check in the list you can still start them as wanted. It does not affect the programs, just makes it load later when required.