The down red arrow in Disk Management

Under Vista, you will find that there is a red down arrow in Disk
Management for a all-new disk.

(Please see the attached picture.)

The reason is that disk is not initiallized. (Still no MBR on it.)

In that time, you can right-click mouse on that disk and choose
"Initialize" in the pop-up menu.
After initializing (MBR of the disk is created) , the red down
arrow will disappear and the disk will become "basic disk".

Before initializing, you CAN NOT create any partition on that disk.