got to your start menu and select RUN and type in misconfig, then select the boot tab then select Advanced and at the top you can select how many cores you have and the reboot your system
it should use all cores to boot your system

sorry... it's no good.

to quote

"Make Vista Use Multiple Cores to Speed Up Boot Time This bogus tip made the rounds recently and almost everybody got caught including Lifehacker and big brother site Gizmodo... although commenters called it out quickly on both sides, and the editors updated the posts. (That's yet another reason to always participate in the comments here.) According to this tip, you were supposed to use MS Config to modify the "Number of processors" drop-down on the Boot tab. The problem is that this setting is only used for troubleshooting and debugging, to be able to determine if there is a problem with a single processor, or for a programmer to test their code against a single core while running on a multi-core system. Windows will use all your processors by default without this setting."

http://lifehacker.com/5033518/debunking-common-windows-performance-tweaking-myths