Here's my take on it.
Start with 3 primary partions and one extended partion. You can have as many logical partitions in the extended partition as you want. Some OSes require a primary partition to install so it's wise to have as many of them as you can, i.e. 3. You never know, you might want them to start mucking about with Linux, *BSD, BeOS, Plan 9 or whatever when you get fed up playing games 🙂
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Personally I wouldn't use W2000 without NTFS, but this would proclude sharing its boot partition with WinME and 98 as the latter two can't grok NTFS. If you keep all the OSes in separate partitions you can easily install multiple copies of the same program but sharing "Program Files" folders and the like can get messy so think about where you install your programs as the default C: won't normally suit. On the other hand installing 98, ME and 2000 in the same FAT32 partition is the easiest way to multi-boot and that's the way M$ expects you to do it.
For any partitions that you indend to use purely for data (ie storing images, mp3s, wav's etc), FAT32 is a good choice (unless you intend to use NT since it can only read NTFS and FAT16). Most modern OSes can read FAT32 easily. Use NTFS where security is important. As it's a journaling filesysem, NTFS is also fast at recovering itself after crashes.
Sizewise, I'd initally make the primary partitions quite small, say about 2 or 3 GB and keep only the bare OS installations on them, as much as possible, so you have plenty of large contiguous space to play with. You don't need to use all your disk right away so think about leaving some unpartitioned space for a rainy day.
On the other-hand, you could go for just one big f*ckoff C: drive 🙂