I have Drive Image Pro 4 which comes with Partition Magic Pro 6 (very slightly different than PM Regular 6), and PM Pro 6 will not even install under XP. When you try it you get "This application has a known problem with this version of windows and will be disabled".
More like this version of windows has a known problem with everything :|
Now you could *try* running PMPro 6 from within Windows ME or even DOS and use it to resize the partitions...I'm not sure how well that would work though...
On the one hand, I've never reformatted my second hard drive to "WinXP NTFS" I was using the drive exactly how it was formatted for Win2000 and WinXP read it just fine.
On the other hand, if PMPro6 won't run under WinXP, I would suggest that it's probably a bad idea to use it to resize XP's drive from a different OS.
While it may work, I would say you do so at your own risk.