Missing disk space after removing Windows XP partition

I installed Apple's Boot Camp beta software on my Mac Pro soon after it was released. This software allows one to run Microsoft Windows on an Intel-based Mac. The Boot Camp Assistant program lets one repartition an existing HFS+ volume, adding a FAT32 or NTFS partition to the disk without damaging the existing HFS+ partition.

I used this software to repartition a 500 GB drive into two equally-sized partitions: one HFS+ partition, and one NTFS partition. I then installed Windows XP SP2 on the NTFS partition. Everything worked fine for a while. But then the Boot Camp volume stopped showing up in the Startup Disk pane of the System Preferences program. What this means is that Startup Disk was no longer seeing a bootable operating system on the NTFS Windows XP partition.

I decided to remove the NTFS partition and add it back again. The Boot Camp Assistant program lets one do this. Unfortunately, things did not go smoothly. After I removed the NTFS partition and rebooted, I was shocked to see that the HFS+ partition had not ben expanded to fill the entire drive.

I used Disk Utility to check the drive. The first time I did this, the program reported the abnormal end of a child process. The second time, the program was succesfully able to repair a minor problem with the volume bit map. However, the problem with the missing disk space remained. The following screenshot illustrates the problem.

Capacity                           465.4 GB
Used space                        -203.6 GB
                                 ---------
What should be available           261.8 GB
What's actually available          -29.4 GB
                                 ---------
What's missing                     232.4 GB

I am sure that reformatting the entire drive would fix the problem, but I would rather not take such a drastic step yet. I haved posted a new topic to Apple's Boot Camp discussion forum, asking for advice.