There are literally half a dozen different ways to extend a volume and here is one more. :)
This Dell utility will expand boot drives on WindowsXP/2000/2003 without downtime.
Its was written for Dell arrays but it works on any volume (Physical or Virtual, System, Boot or Data).
Quick download and no installation which I like.
Grab it here : Dell ExtPart
Fast, Clean, Free and Simple to use.