My Book Essential II 4TB not opening in other PC

Hi, I have a 4tb WD External Hard Disk and installed it on my Core 2 Quad Pc Windows 7 platform. After I transferred all my files & data (capacity 3.5 TB) everything is working fine. I’m just wondering how can I open my External HDD in other PC, its showing in the device manager but the drive itself is not accessible. I already installed the proper updated software in the other PC, when I tried to access it through the WD device manager it says that I need to format it to NTFS to be recognized? I don’t want to do that really… I thought it was just plug & play… Please help…