partitioning - NTFS partition no longer read on Windows 7

I have a 500 GB external drive that I use with my Windows 7 PC and Snow Leopard laptop. It has the following 4 partitions:

 1. Leopard Installer (HFS+)
 2. Backup (HFS+)
 3. Snow Leopard Installer (HFS+)
 4. Storage (NTFS)

1 and 3 contain Mac OS X install CD images in case of any problems, and 2 contains a bootable backup of my entire Mac. The last partition is the one I store movies, music and docs on. The PC recognizes only partition 4, while the Mac recognizes all 4, which is perfect. All this is with the GUID Partition Table (GPT). But since its recognized on both Macs and PCs, I'm guessing it uses something like a hybrid MBR. I don't know what that means, but I remember having to do a lot adjustment to get it to play well with both my computers.

However, I no longer needed the leopard installer, so I erased that partition using disk utility, and formatted it with exFAT, and then again with normal FAT, so that I could use it with my fonera. Now, the Windows PC recognizes the FAT partition, but not the NTFS one it used to. It shows up in Disk Management as Unallocated space, but EASEUS partition manager can read the files off it, and the Mac recognizes it fine.

Any ideas about what's wrong or how I can fix it?

Update (diskpart.exe output):

Microsoft DiskPart version 6.1.7601

DISKPART> list disk


  Disk ###  Status         Size     Free     Dyn  Gpt
  --------  -------------  -------  -------  ---  ---
  Disk 0    Online           37 GB  2048 KB        *
  Disk 1    Online          149 GB      0 B
  Disk 2    Online          465 GB      0 B

DISKPART> select disk=2

Disk 2 is now the selected disk.


DISKPART> list partition

  Partition ###  Type              Size     Offset
  -------------  ----------------  -------  -------
  Partition 1    Primary            200 MB    512 B
  Partition 2    Primary             10 GB   201 MB
  Partition 3    Primary            116 GB    11 GB
  Partition 4    Primary             17 GB   128 GB

It's not listing the 300 or so GB Storage partition.

Answer

You changed the partition table when you erased the second partition, and confused the heck out of Windows. Your easiest (!) way to fix this is to move the files off the NTFS partition, recreate it, and move the files back.

You must do this in Windows 7.

For future reference, I'd put the NTFS partition first or second on the drive. I think there are partition boundaries you are playing with that caused the confusion (and changing the disk order of recognisable partitions in Windows), despite Microsoft's promises otherwise, but I may be wrong.

My reason for stating this is as follows: I have a Mac with one hard drive, partitioned into three drives. First is the main OS X partition, second is a second OS X partition for testing (I'm under NDA so I can't tell you what's there), and third is my Windows 7 under Boot Camp. When I created the second OS X partition for testing, Disk Utility warned me that Boot Camp may no longer work because I was changing the partition table.