Your CPU has very little to do with startup times - that is nearly entirely down to the hard drive you are using. The easiest way to get an instant improvement is to upgrade your boot drive to an SSD. If that is not an option then you can try the following:
On XP: Click Start Button, Select Run, Type "msconfig" (no quotes) and press enter
On Win7 / Vista: Click Start Button, Type "msconfig" (no quotes) inside the search box and press enter.
Select the Startup tab in the box that appears and untick any items that you do not need to load at startup. Nothing in the list is essential to your system so you can't break anything by making changes here - and you can always re-enable something later using the same method if necessary. When you are done click apply / OK etc. This will reduce the number of programs loading at boot and speed up your startup - though how noticibly will depend on the specific programs in question
