A possibility is that the HDD has hidden partition(s) that prevent the HDD from working. Here is what I did:
1) open cmd.exe with administrator privleges
2) type "diskpart"
3) type "list disk". Now, there should be numerous hard disks shown, select the one with your external HDD
4) type "select disk #", with # being the number of the HDD you want to check
5) type " list partition"
If there is indeed a small partition (should be around 100MB-200MB in size) you have to get rid of it. If you have it tell me so I can write the rest you have to do.
MultiMAN and WebMAN Mod (or WebMAN + prepNTFS) support NTFS. But it has its issues and I don't see a reason to use NTFS.
Cheers!