Michael, I have not used it but how about http://www.paragon-software.com/home/camptune/

Here is what they say about their product

"Are you running Windows® XP on your Mac® for compatibility reasons? Then you benefit twice. From the solid Mac hardware and operating system on the one hand and the wide range of software products under MS Windows on the other. With Apple’s release of Boot Camp™ almost all barriers between MS Windows and Mac® OS X have been removed. Paragon is about to break one of the last few remaining.

Until now installation of Windows with Boot Camp made it impossible to resize the Windows partition afterwards. So when running out of space in one of your partitions (the Mac system partition as well as the Windows partition) you had to back up the Windows files, remove the partition with Boot Camp (it would automatically delete the Windows partition and then make the Mac partition the size of the entire hard disk), re-launch the Boot Camp to create a new partition for Windows of the required size, install Windows from scratch, and finally restore the previously backed up files. This procedure would not only cost you time and effort but also proved to be highly delicate.

With Paragon’s CampTune this kind of problems are history. Just insert the CD, reboot the system, resize the partitions by moving the controller and click Apply - that´s it! "