Use the start up manager to determine how many programs are automatically loading. Too many unnecessary programs will really slow down the start up time
Open Task Manager by right clicking on an empty space near the clock and click 'task manager'. Click 'more details' in the task manager and then click the 'start up' tab. Untick any program that you don't need to start automatically. BEWARE, only untick programs if you know what they are and you know they are not essential to the boot up of the PC.
You don't need browsers, office suites, spotify, youtube to start automatically, for example, but you do need your antivirus.