Windows 7 / XP Dual Boot - Partition suggestions?

Can anyone suggest or recommend a good partition scheme to have when dual booting XP (x86) and Win7 (x64)?

With XP, I used nlite and had a VERY customized partitioning scheme that had programs on one partition, music on another, video and pictures on another, and "My Documents" on yet another. I wanted to keep partition sizes small for indexing purposes and to preserve data in partition got corrupt for whatever reason.

But, I realize, I went overboard.

I've got 4 hard drives:
320gb x2
640gb x2

I'd like to keep the system / data partitions SEPARATE from user data as much as possible. I'd also prefer to keep program files data on a separate partition, but I've heard this is not advisable and can lead to buddy systems. Can anyone confirm this?

I'd like suggestions on how people would partition in my instance. Right now, I have XP / Win7 partitions on one of the 320gb drives. The other 320gb drive is split in half. One of the 640 drives is just one big partition and the other is also split in half.

What would you guys do? And I'd like to keep it as simple as possible while at the same time, keeping personal / user / program data on separate partitions.

Ideas?

* I will post a pic of my Disk Management partition table for reference when I get home from work *