One of the major factor that affect the performance of the system particularly the booting time of the system is the number of start up items. If you have many softwares installed then they may create start up items on your system.
More the start up items means more the boot time. So try to reduce the start up items. Here are the steps to do so.
To see the start up items currently on your system type "msconfig" in the run menu and click on OK.
You can also go through Control Panel-->Administrative Tools-->System Configuration
You will find the System Configuration Window. Do not do any changes in the General and Boot tabs. I will tell the detail use of all the tabs in a special chapter dedicated to system Configuration window.
To see start up items click on the "Startup" tab. You can see the list of startup programs in your system.
To disable or enable all the startup items click on "Disable All" or "Enable All" respectively.
If you want to keep some important startup programs like the anti viruses, spy-wares, etc, then mark the check box beside them them and to disable a particular item uncheck the check box beside them.
Then click on the Apply button to make the changes.
Note:-You must have administrative access to the system to use System Configuration