One of the Main Reason that slow down the startup speed is the "Huge list of Startup Programmes". Some programme by default create a startup entry, such as Yahoo Messenger, Windows Live Messenger Skype etc.. It is not possible to find all your startup programme if you Go Start > Programmes > Startup. If you can disable unwanted startup programmes, your computer's start up speed will increase. please do as follows.

Press Win Key + R or Start > Run

Type msconfig presss ok

'System Configuration Utility' will open. Click on "Startup" Tab
That's where you will see the huge list of Start up Programme. You can get more detail of a Particular Programme by looking at Command and Location

What to Disable and What not to Disable?

In fact you can disable all Programme, But we recommand you to keep the Programme such as Antivirus, Spy ware removal Programme. If you have Norton Anti-vius Programme installed in your computer.
Click on Service Tab

Check "Hide Microsoft Srevices" Now Disable all the service, except the service you want to run background when computer start up such Antivirus, Spyware Removal and Firewall Software.

After you have completed the work with disabling start up Programme and services, Press Ok. You will be asked to restart the Computer. When you start the computer next time, you will get Notification window about your "System Configuration Utility". You 'check' not to show this notification again and press ok. That's it.