Difficulty Assigning Drive Letters

Last weekend I installed a new boot drive after months of intermittent
problems. I used Macrium Reflect to image my two booting partitions
onto the new drive. I was anticipating a huge fight but it went
amazingly well. I bought a larger drive this time 1T. About half of it
was left after I partitioned for the XP and Win7. With both booting
successfully I decided to use the remainder of the drive for data
partitions. I made two equal size partitions, using Win7 Disk
Management. The first one insisted on being a Primary partition, I
couldn't find a way to make it anything else??? I wanted to use drive
letters that followed the letters on my other data drive, so 'N' and
'O'. When I booted XP I went to its Disk Management. XP had decided to
call them 'E' and 'F'. The second partition, which Win7 had deigned to
desigate a logical drive, renamed no problem to 'O'. But the primary
partition that Win7 had made drove XP Disk Management into lala land
when I tried to rename it, and it took forever for XP to close down
after my attempt.
So.... I guess I want to make two logical drives, instead of one that
is a primary, in order to name them the same letter in both OS's.
Or a way to defeat XP's naming hangup? I kind of thought I wanted to
do my partitioning in Win7, to keep the boundaries right (or
something). Anybody have ideas about the best way to approach this?