I am assuming that you originally formatted these drives on an Intel Mac (OS X) system.
Rather than paraphrasing what I've heard in other places I'll simply quote from the Wikipedia article for EFI System partition.
On Apple–Intel architecture Macintosh computers, the EFI partition is initially blank and not used for booting.
However, the EFI partition is used as a staging area for firmware updates; specifically it places a firmware flash utility (EFI binary) and data file (FD – "Firmware Device") in the directory EFI/APPLE/FIRMWARE which is then run when rebooting the system in "flash firmware" mode.
If deleted, the system will still boot, and the boot manager will still allow users to choose whether to start a Boot Camp partition or the default Mac OS X, but firmware updates will fail.
As I believe has been pointed out in other answers, the EFI partition is not used by Windows 7 and is not created when using a system which does not use EFI. In other words, if you are not going to use these drives as anything other than data drives then, yes, you can delete the EFI partition.
I'm afraid I did not take the time to experiment and find out if deleting the EFI partition will resolve the problems you are having with Windows 7 "seeing" your NTFS partitions on the drive. But it seems like it would be worth trying.
If I recall correctly you will not be able to delete the EFI partition from the Windows
Disk Management utility. One way you could delete the EFI partition(s) is by running
DISKPART from a (elevated) Window's command prompt.
I do this by first selecting the partition I want to delete and then verifying that I've selected the correct partition. Below is an example with one of my drives.
After you are sure you have selected the partition you want to delete, the command
delete part override
should delete it.
(If you don't care about any of the data on the drive and just want to repartition it, you could also use the
clean command. For more info about it, type
HELP CLEAN in
Hope this helps.
DISKPART> list disk
Disk ### Status Size Free Dyn Gpt
-------- ------------- ------- ------- --- ---
Disk 0 Online 76 GB 0 B
Disk 1 Online 372 GB 32 GB
Disk 2 Online 465 GB 0 B
Disk 3 Online 931 GB 0 B
Disk 4 Online 149 GB 255 MB *
DISKPART> select disk 4
Disk 4 is now the selected disk.
DISKPART> list part
Partition ### Type Size Offset
------------- ---------------- ------- -------
Partition 1 System 200 MB 20 KB
Partition 2 Unknown 37 GB 200 MB
Partition 3 Unknown 111 GB 37 GB
DISKPART> select part 1
Partition 1 is now the selected partition.
DISKPART> detail part
Type : c12a7328-f81f-11d2-ba4b-00a0c93ec93b
Hidden : Yes
Attrib : 0000000000000000
Offset in Bytes: 20480
Volume ### Ltr Label Fs Type Size Status Info
---------- --- ----------- ----- ---------- ------- --------- --------
* Volume 15 EFI FAT32 Partition 200 MB Healthy Hidden