You usually install the oldest operating system first so, XP, XP x64, 7-32, 7-64 would by the order I would use. You said you wanted a D:\ data drive - one drive common to all four operating systems or a D:\ drive for each operating system? The first would require five partitions, the second eight; so which is it? I would recommend you create all of the partitions prior to installing any of the operating systems and format all as NTFS. The above comment about primary partitions is incorrect; I have a 1Tb drive divided into four partitions - one primary with XP Pro, and three logical on the extended partition with XP Pro x64, Win7 32 and Win7 64. No drives/partitions are hidden so I can't provide and answer for that option.