What causes this partition discrepancy between GParted and Disk Management?

Question

Here's a screenshot of my partition layout as seen by GParted:

There are three primary partitions and an extended partition (it's a MBR disk) that contains two logical disks, some unallocated space and one more logical disk.

Now, here's the same disk as seen by Windows:

Four primary partitions, then an extended partition containing one logical disk and unallocated space, then one more primary partition. That's 6 top-level partitions, while MBR allows only four.

What causes this anomaly? How can I diagnose it? How can I fix it?

Here's fdisk -l output:

Disk /dev/sda: 298,1 GiB, 320072933376 bytes, 625142448 sectors
Units: sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disklabel type: dos
Disk identifier: 0x7a675f3e

Device     Boot     Start       End   Sectors   Size Id Type
/dev/sda1            2048  83888127  83886080    40G 83 Linux
/dev/sda2        83888128  92276735   8388608     4G 83 Linux
/dev/sda3  *     92276736 251660287 159383552    76G  7 HPFS/NTFS/exFAT
/dev/sda4       251660288 625141759 373481472 178,1G  5 Extended
/dev/sda5       251662336 293605375  41943040    20G 83 Linux
/dev/sda6       293607424 377493503  83886080    40G  7 HPFS/NTFS/exFAT
/dev/sda7       608364544 625141759  16777216     8G 83 Linux

Additional information:

• All partitions except sda6 were created under Linux before Windows was installed. sda6 (the sole logical disk detected by Windows) was created later using Disk Management. It already displayed all partitions as primary prior to that.
• When I installed Windows to sda3, sda5 disappeared from the partition table. It wasn't wiped, when I recreated it without formatting the data was still there. Then I installed Windows on sda3 again and sda5 disappeared, just like before.
• Windows detects this disk as MBR.
• It's Windows 7 Professional 32-bit with all updates installed.