Vista has a feature of utilizing the hard drive to its max, but in the event of power failure, there are chances of data loss....thats why this feature is turned off.....But if you got some backup power through UPS, you can enable this feature.....
Note: try this only if you got an UPS for auxilary power.
1)Right click on My Computer icon on the desktop and click properties. Click on device manager.
2) click on the little plus sign in front of Disk drives to display your hard drive(s).
3)choose the hard drive you want to optimize.Right click on it and click properties.
4)Click the Policies tab.
5)Check the Enable advanced performance box and click OK.