How to create several partitions on an external hard, recognizable by both windows and mac? I have an external hard drive, which already has a bootable partition for a Snow Leopard installation disk, and a bootable partition for Mavericks, both created with Mac OS X and working fine in Windows and Mac. 

I want to create one NTFS partition and one FAT32 partition on this external hard as well but cannot.

If I create it in GUID, for the sum of sizes of FAT32 and NTFS partition I get one unallocated partition in Windows. If I do it in Windows, it shows on the Mac but the content are not there.

Inspecting the hard in a partitioning tool in Windows shows that there is a 200MB hidden partition on the hard drive as well (type: primary), so I guess the problem is with the maximum 4 primary partitions limitation of MBR.

Any suggestions?
It might be difficult to re-partition your disk from outside the Mavericks boot without destroying it. So I would use the Mavericks' Disk Utility to do this. And make sure you have everything backup because this looks like a difficult task.

This 200Mb partition you're seeing is probably the EFI boot partition, Mac OS X needs it to boot. Since you're booting Mac OS X, you cannot use a MBR partition scheme, I doubt Disk Utility will even let you change it. You'll have to stay in GUID

In Disk Utility, you can create as many partitions as you want, except for NTFS partitions which are not natively supported by Mac OS X (you can read, but not write). You can create FAT32 or exFAT, which have the advantage of being readable and writable by windows, mac and linux. FAT32 technically has a limit of 2TB partition, but I've managed to make it work on one of my hard-drive anyway.
You can read up on different filesystems on here.

Any reasons you're keeping the Snow Leopard installation disk? That sounds like more trouble and wasted hard-drive space, unless you actively need it.