trying to connect 4 HDs with total capacity of +2tb -Issue

I have 4 external hard disks with total capacity of + 2TBs - when i plug the 4th hard disk on my windows 8 3 of my hard disks disappear and only one is displayed?

What seems to be the problem?

worth to say also I'm running windows 8 - 64 bit

Sometimes Windows get confused if there's a conflict with Drive letters of the drives. Open Disk Management and look at each disk to see if there's a letter assigned to each of them. If not, right click on it and select Change Drive letter and Paths

To open disk management: Win+X->Disk Management.