If that is the recovery partition inserted by the manufacturer, the simple answer is you shouldn't. The partition is protected so you don't accidentally modify the contents and is usually just larger than what's actually needed to store the data. You could use a third-party partitioning tool to shrink it, but it's somewhat risky. Instead, I'd burn a set of recovery discs from that partition using the manufacturer's burning tool found in the Start menu and then duplicate the discs for a backup. You can then safely wipe the partition as you'll have two working copies of the contents.
John
i have vista premiun and i want to resize drive D recovery image because it takes so much space in my computer, any idea how to do that.

Chowhound
Comic Vine
GameFAQs
GameSpot
Giant Bomb
TechRepublic