I came across this tweak to enable vista startup to use multiple core but not sure if is really works.. not yet try out... will try it after getting back from work...

1. Click on Start then type "MSCONFIG" hit enter then click continue through the UAC we talked about earlier. This opens a small screen containing some interesting startup options, playing with this will allow you to start and stop most things that run in the background. The startup tab tells you which company each service belongs to so you can use this to try and slim up your startup. One of the biggest impacts you can perform to your cold boot is in unlocking the potential of your new machine.

2. Select the boot tab, then choose advanced options...

3. Check off Number of processors, and set that drop down box to the highest available number.

What this is doing is unlocking Windows Vistas ability to use multiple cores to start up. When Vista was designed in order to make it compatible with older hardware this option was set to (1) so that it will always use only one core. By unlocking it you allow Vista to boot using all of your cores this can lead to a boot time performance increase of 15-40% for a cold boot and about 10% for a warm boot or a return from standby.