Try this Ayisha,
1] Goto Start > All Programs > Startup, delete any of the shortcuts there for programs you do not want to start on startup. These are shortcuts only, so deleting them will not delete the full programs.
2] Goto Start > Run and type in "msconfig", (without the quotes), and click OK.
In the "System Configuration Utility" window that displays, click the Startup tab. Here you can remove the tick for any programs that you do not want to start on startup. Be careful, some of these are needed, eg your anti-virus, and firewall if you use a third party software firewall.
When you click apply, then OK, you will be asked to restart your computer, and when you do, you will get an information box stating that you are on Selective Startup. You can stop that window from displaying each time you startup within the window itself.
3] If you have a number of icons in your System tray, (the notification area next to your clock), hover the mouse cursor over each to find out what program the icon is for, then find that program and goto it's Tools and/or Options and remove the option to start on startup. Alternatively you can double click the icon to bring up the program.
Good luck, and hope this is useful.