Partition HD for triple boot (or move Apple_Boot Recovery HD from a primary partition)
You're getting confused between the MBR and GPT partitioning schemes. Intel Macs generally use GPT, but for Boot Camp, they also add a so-called Hybrid MBR for booting Windows, which duplicates all or some of the partition entries. GPT can have a large number of partitions (typically, enough space is reserved for 128 partitions), but as MBR only supports 4, if you have more than that, you can't represent all of them in the MBR. Note that one partition of the EFI type 0xEE is required - this normally covers the whole disk, but for hybrid MBR, it usually only covers the GPT itself and the 200MB EFI partition at the start of the disk. So that gives you 3 usable MBR partitions, which Windows will see.

You don't mention what your third OS should be for triple-boot; if it's another installation of OS X, you have nothing to worry about. Just install it as normal, it will use GPT entries 5+. If you want another BIOS-based OS, such as Windows or most Linux distros, you'll probably need to mess with the hybrid MBR yourself. I'd do all the partitioning in OSX's Disk Utility, as it will update both the GPT and MBR tables simultaneously. Just make the new Windows or Linux partition FAT32 to begin with. Then, if your MBR covers the Recovery HD but has no entry for your new partition, get the exact positions and sizes of the GPT partitions using

sudo gpt -r disk0


This should list all 5 partitions.

In fdisk (or so), delete the MBR version of the Recovery HD, and create a new partition with the exact position and size of your new (5th) partition. Windows should now see this partition instead of the Recovery HD. You can change its type, format it, etc. as usual. Just don't try to resize it from fdisk or Windows Generally, make sure that all partitions that exist in the MBR except the 0xEE EFI partition map exactly onto a GPT partition.

This is all a bit dangerous so make sure you have backups of everything.