The simplest way to fix a sluggish PC boot is to reduce the number of apps that launch on startup, as having too many programs running when the computer boots makes the entire process much slower, especially on older hardware.
To remove those apps, press Control+Alt+Delete, then select Task Manager, then click the More Details link. Select the Startup tab from this menu. This section contains a list of all the apps that run when your computer boots up. Examine the list of enabled apps and remove any that you don't need – you can disable an app by right-clicking on it and selecting Disable.
Mind you, don't turn off Microsoft services or critical apps like antivirus. If you're not sure whether it's a good idea to disable an app, look it up on Google.