PerfectDisk can shrink MFT reserved zone on active drive but not logical drive

Windows XP SP3, PerfectDisk Pro 13

I created a new logical partition on my hard drive (E:\ NTFS) and tried to shrink the MFT reseved zone with Perfectdisk boot-time defrag, but it won't work. I've been using PD to shrink the MFT on the active partition (C:\ NTFS) on my comuter and others for some time and it's always worked. Out of curiosity, I tried the Diskeeper 12 free trial but it wouldn't work on my logical partition either. Just wondering if anyone has an explanation for this? I know it's not really necessary to shrink the MFT, I just like doing it anyway.